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• iOS Support with Windows Azure Mobile Services – now with Push Notifications

  - by ScottGu

  A few weeks ago I posted about a number of improvements to Windows Azure Mobile Services. One of these was the addition of an Objective-C client SDK that allows iOS developers to easily use Mobile Services for data and authentication.  Today I'm excited to announce a number of improvement to our iOS SDK and, most significantly, our new support for Push Notifications via APNS (Apple Push Notification Services).  This makes it incredibly easy to fire push notifications to your iOS users from Windows Azure Mobile Service scripts. Push Notifications via APNS We've provided two complete tutorials that take you step-by-step through the provisioning and setup process to enable your Windows Azure Mobile Service application with APNS (Apple Push Notification Services), including all of the steps required to configure your application for push in the Apple iOS provisioning portal: Getting started with Push Notifications - iOS Push notifications to users by using Mobile Services - iOS Once you've configured your application in the Apple iOS provisioning portal and uploaded the APNS push certificate to the Apple provisioning portal, it's just a matter of uploading your APNS push certificate to Mobile Services using the Windows Azure admin portal: Clicking the “upload” within the “Push” tab of your Mobile Service allows you to browse your local file-system and locate/upload your exported certificate.  As part of this you can also select whether you want to use the sandbox (dev) or production (prod) Apple service: Now, the code to send a push notification to your clients from within a Windows Azure Mobile Service is as easy as the code below: push.apns.send(deviceToken, {      alert: 'Toast: A new Mobile Services task.',      sound: 'default' }); This will cause Windows Azure Mobile Services to connect to APNS (Apple Push Notification Service) and send a notification to the iOS device you specified via the deviceToken: Check out our reference documentation for full details on how to use the new Windows Azure Mobile Services apns object to send your push notifications. Feedback Scripts An important part of working with any PNS (Push Notification Service) is handling feedback for expired device tokens and channels. This typically happens when your application is uninstalled from a particular device and can no longer receive your notifications. With Windows Notification Services you get an instant response from the HTTP server.  Apple’s Notification Services works in a slightly different way and provides an additional endpoint you can connect to poll for a list of expired tokens. As with all of the capabilities we integrate with Mobile Services, our goal is to allow developers to focus more on building their app and less on building infrastructure to support their ideas. Therefore we knew we had to provide a simple way for developers to integrate feedback from APNS on a regular basis.  This week’s update now includes a new screen in the portal that allows you to optionally provide a script to process your APNS feedback – and it will be executed by Mobile Services on an ongoing basis: This script is invoked periodically while your service is active. To poll the feedback endpoint you can simply call the apns object's getFeedback method from within this script: push.apns.getFeedback({       success: function(results) {           // results is an array of objects with a deviceToken and time properties      } }); This returns you a list of invalid tokens that can now be removed from your database. iOS Client SDK improvements Over the last month we've continued to work with a number of iOS advisors to make improvements to our Objective-C SDK. The SDK is being developed under an open source license (Apache 2.0) and is available on github. Many of the improvements are behind the scenes to improve performance and memory usage. However, one of the biggest improvements to our iOS Client API is the addition of an even easier login method.  Below is the Objective-C code you can now write to invoke it: [client loginWithProvider:@"twitter"                     onController:self                        animated:YES                      completion:^(MSUser *user, NSError *error) {      // if no error, you are now logged in via twitter }]; This code will automatically present and dismiss our login view controller as a modal dialog on the specified controller.  This does all the hard work for you and makes login via Twitter, Google, Facebook and Microsoft Account identities just a single line of code. My colleague Josh just posted a short video demonstrating these new features which I'd recommend checking out: Summary The above features are all now live in production and are available to use immediately.  If you don’t already have a Windows Azure account, you can sign-up for a free trial and start using Mobile Services today. Visit the Windows Azure Mobile Developer Center to learn more about how to build apps with Mobile Services. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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• Examine your readiness for managing Enterprise Private Cloud

  - by Anand Akela

  Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Cloud computing promises to deliver greater agility to meet demanding  business needs, operational efficiencies, and lower cost. However these promises cannot be realized and enterprises may not be able to get the best value out of their enterprise private cloud computing infrastructure without a comprehensive cloud management solution . Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Times New Roman","serif";} Take this new self-assessment quiz that measures the readiness of your enterprise private cloud. It scores your readiness in the following areas and discover where and how you can improve to gain total cloud control over your enterprise private cloud. Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Complete Cloud Lifecycle Solution Check if you are ready to manage all phases of the building, managing, and consuming an enterprise cloud. You will learn how Oracle can help build and manage a rich catalog of cloud services – whether it is Infrastructure-as-a-Service, Database-as-a-Service, or Platform-as-a-Service, all from a single product. Integrated Cloud Stack Management Integrated management of the entire cloud stack – all the way from application to disk, is very important to eliminate the integration pains and costs that customers would have to otherwise incur by trying to create a cloud environment by integrating multiple point solutions. Business-Driven Clouds It is critical that an enterprise Cloud platform is not only able to run applications but also has deep business insight and visibility. Oracle Enterprise Manager 12c enables creation of application-aware and business-driven clouds that has deep insight into applications, business services and transactions. As the leading providers of business applications and the middleware, we are able to offer you a cloud solution that is optimized for business services. Proactive Management Integration of the enterprise cloud infrastructure with support can allow cloud administrators to benefit from Automatic Service Requests (ASR), proactive patch recommendations, health checks and end-of-life advisory for all of the technology deployed within cloud. Learn more about solution for Enterprise Cloud and Cloud management by attending various sessions , demos and hand-on labs at Oracle Open World 2012 . Stay Connected: Twitter |  Face book |  You Tube |  Linked in |  Newsletter

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• How to disable or tune filesystem cache sharing for OpenVZ?

  - by gertvdijk

  For OpenVZ, an example of container-based virtualization, it seems that host and all guests are sharing the filesystem cache. This sounds paradoxical when talking about virtualization, but this is actually a feature of OpenVZ. It makes sense too. Because only one kernel is running, it's possible to benefit from sharing the same pages of filesystem cache in memory. And while it sounds beneficial, I think a set up here actually suffers in performance from it. Here's why I think why: my machines aren't actually sharing any files on disk so I can't benefit from this feature in OpenVZ. Several OpenVZ machines are running MySQL with MyISAM tables. MyISAM relies on the system's filesystem cache for caching of data files, unlike InnoDB's buffer pool. Also some virtual machines are known to do heavy and large I/O operations on the same filesystem in the host. For example, when running cat *.MYD > /dev/null on some large database in one machine, I saw the filesystem cache lowering in another, monitored by htop. This essentially flushes all the useful filesystem cache in guests (FIFO) and so it flushes the MySQL caches in the guests. Now users are complaining that MySQL is very slow. And it is. Some simple SELECT queries take several seconds on times disk I/O is heavily used by other machines. So, simply put: Is there a way to avoid filesystem cache being wiped out by other virtual machines in container-based virtualization? Some thoughts: Choosing algorithm for flushing filesystem cache in the kernel. (possible? how?) Reserving a certain amount of pages for a single VM. (seems no option for filesystem cache type of pages that reading man vzctl) Will running MySQL on another filesystem get me anywhere? If not, I think my alternatives are: Use KVM for MySQL-MyISAM running VMs. KVM actually assigns memory to the VM and does not allow swapping out caches unless using a balloon driver. Move to InnoDB and tune the buffer pools, dirty pages, etc. This is now considered to be 'nice to have' on the long-term as not everyone responsible for administration of the system understands InnoDB. more suggestions welcome. System software: Proxmox (now 1.9, could be upgraded to 2.x). One big LV assigned for the VMs.

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• Monitoring tools that can take high rate and high volume?

  - by Jon Watte

  We're using Cacti with RRDTool to monitor and graph about 100,000 counters spread across about 1,000 Linux-based nodes. However, our current setup generally only gives us 5-minute graphs (with some data being minute-based); we often make changes where seeing feedback in "near real time" would be of value. I'd like approximately a week of 5- or 10-second data, a year of 1-minute data, and 5 years of 10-minute data. I have SSD disks and a dual-hexa-core server to spare. I tried setting up a Graphite/carbon/whisper server, and had about 15 nodes pipe to it, but it only has "average" for the retention function when promoting to older buckets. This is almost useless -- I'd like min, max, average, standard deviation, and perhaps "total sum" and "number of samples" or perhaps "95th percentile" available. The developer claims there's a new back-end "in beta" that allows you to write your own function, but this appears to still only do 1:1 retention (when saving older data, you really want the statistics calculated into many streams from a single input. Also, "in beta" seems a little risky for this installation. If I'm wrong about this assumption, I'd be happy to be shown my error! I've heard Zabbix recommended, but it puts data into MySQL or some other SQL database. 100,000 counters on a 5 second interval means 20,000 tps, and while I have an SSD, I don't have an 8-way RAID-6 with battery backup cache, which I think I'd need for that to work out :-) Again, if that's actually something that's not a problem, I'd be happy to be shown the error of my ways. Also, can Zabbix do the single data stream - promote with statistics thing? Finally, Munin claims to have a new 2.0 coming out "in beta" right now, and it boasts custom retention plans. However, again, it's that "in beta" part -- has anyone used that for real, and at scale? How did it perform, if so? I'm almost thinking about using a graphing front-end (such as Graphite) and rolling my own retention backend with a simple layer on top of mmap() and some stats. That wouldn't be particularly hard, and would probably perform very well, letting the kernel figure out the balance between frequency of flushing to disk and process operations. Any other suggestions I should look into? Note: it has to have shown itself able to sustain the kinds of data loads I'm suggesting above; if you can point at the specific implementation you're referencing, so much the better!

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• Content in Context: The right medicine for your business applications

  - by Lance Shaw

  For many of you, your companies have already invested in a number of applications that are critical to the way your business is run. HR, Payroll, Legal, Accounts Payable, and while they might need an upgrade in some cases, they are all there and handling the lifeblood of your business. But are they really running as efficiently as they could be? For many companies, the answer is no. The problem has to do with the important information caught up within documents and paper. It’s everywhere except where it truly needs to be – readily available right within the context of the application itself. When the right information cannot be easily found, business processes suffer significantly. The importance of this recently struck me when I recently went to meet my new doctor and get a routine physical. Walking into the office lobby, I couldn't help but notice rows and rows of manila folders in racks from floor to ceiling, filled with documents and sensitive, personal information about various patients like myself.  As I looked at all that paper and all that history, two things immediately popped into my head.  “How do they find anything?” and then the even more alarming, “So much for information security!” It sure looked to me like all those documents could be accessed by anyone with a key to the building. Now the truth is that the offices of many general practitioners look like this all over the United States and the world.  But it had me thinking, is the same thing going on in just about any company around the world, involving a wide variety of important business processes? Probably so. Think about all the various processes going on in your company right now. Invoice payments are being processed through Accounts Payable, contracts are being reviewed by Procurement, and Human Resources is reviewing job candidate submissions and doing background checks. All of these processes and many more like them rely on access to forms and documents, whether they are paper or digital. Now consider that it is estimated that employee’s spend nearly 9 hours a week searching for information and not finding it. That is a lot of very well paid employees, spending more than one day per week not doing their regular job while they search for or re-create what already exists. Back in the doctor’s office, I saw this trend exemplified as well. First, I had to fill out a new patient form, even though my previous doctor had transferred my records over months previously. After filling out the form, I was later introduced to my new doctor who then interviewed me and asked me the exact same questions that I had answered on the form. I understand that there is value in the interview process and it was great to meet my new doctor, but this simple process could have been so much more efficient if the information already on file could have been brought directly together with the new patient information I had provided. Instead of having a highly paid medical professional re-enter the same information into the records database, the form I filled out could have been immediately scanned into the system, associated with my previous information, discrepancies identified, and the entire process streamlined significantly. We won’t solve the health records management issues that exist in the United States in this blog post, but this example illustrates how the automation of information capture and classification can eliminate a lot of repetitive and costly human entry and re-creation, even in a simple process like new patient on-boarding. In a similar fashion, by taking a fresh look at the various processes in place today in your organization, you can likely spot points along the way where automating the capture and access to the right information could be significantly improved. As you evaluate how content-process flows through your organization, take a look at how departments and regions share information between the applications they are using. Business applications are often implemented on an individual department basis to solve specific problems but a holistic approach to overall information management is not taken at the same time. The end result over the years is disparate applications with separate information repositories and in many cases these contain duplicate information, or worse, slightly different versions of the same information. This is where Oracle WebCenter Content comes into the story. More and more companies are realizing that they can significantly improve their existing application processes by automating the capture of paper, forms and other content. This makes the right information immediately accessible in the context of the business process and making the same information accessible across departmental systems which has helped many organizations realize significant cost savings. Here on the Oracle WebCenter team, one of our primary goals is to help customers find new ways to be more effective, more cost-efficient and manage information as effectively as possible. We have a series of three webcasts occurring over the next few weeks that are focused on the integration of enterprise content management within the context of business applications. We hope you will join us for one or all three and that you will find them informative. Click here to learn more about these sessions and to register for them. There are many aspects of information management to consider as you look at integrating content management within your business applications. We've barely scratched the surface here but look for upcoming blog posts where we will discuss more specifics on the value of delivering documents, forms and images directly within applications like Oracle E-Business Suite, PeopleSoft Enterprise, JD Edwards Enterprise One, Siebel CRM and many others. What do you think?  Are your important business processes as healthy as they can be?  Do you have any insights to share on the value of delivering content directly within critical business processes? Please post a comment and let us know the value you have realized, the lessons learned and what specific areas you are interested in.

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• Should use EXT4 or XFS to be able to 'sync'/backup to S3?

  - by Rafa

  It's my first message here, so bear with me... (I have already checked quite a few of the "Related Questions" suggested by the editor) Here's the setup, a brand new dedicated server (8GB RAM, some 140+ GB disk, Raid 1 via HW controller, 15000 RPM) it's a production web server (with MySQL in it, too, not just serving web requests); not a personal desktop computer or similar. Ubuntu Server 64bit 10.04 LTS We have an Amazon EC2+EBS setup with the EBS volume formatted as XFS for easily taking snapshots to S3, via AWS' console. We are now migrating to the dedicated server and I want to be able to backup our data to Amazon's S3. The main reason being the possibility of using the latest snapshot from an EC2 instance in case of hardware failure on the dedicated server. There are two approaches I am thinking of: do a "simple" file-based backup with rsync, dumping the database' and other files, and uploading to amazon via S3 API commands, or to an EC2 instance, or something. do a file-system "freeze" (using XFS) with the usual ebs/ec2 snapshot tool to take part of the file system, take a snapshot, and upload it to Amazon. Here's my question (or series of questions): Can I safely use XFS for the whole system as the main and only format on the dedicated server? If not, is it safe to use EXT4? Or should I use something else? would then be possible to make snapshots of the system to upload to Amazon? Is it possible/feasible/practical to do what I want to do, anyway? any recommendations? When searching around for S3/EBS/XFS, anything relevant to my problem is usually focused on taking snapshots of a XFS system that is already an EBS volume. My intention is to do it in a "real"/metal dedicated server. Update: I just saw this on Wikipedia: XFS does not provide direct support for snapshots, as it expects the snapshot process to be implemented by the volume manager. I had always assumed that I could choose 2 ways of doing snapshots: via LVM or via XFS (without LVM). After reading this, I realize these 2 options are more like it: With XFS: 1) do xfs_freeze; 2) copy the frozen files via, eg, rsync; 3) unfreeze xfs With LVM and XFS: 1) do xfs_freeze; 2) make a binary copy of the frozen fs via lvcreate and related commands; 3) unfreeze xfs; 4) somehow backup the LVM snapshot. Thanks a lot in advance, Let me know if I need to clarify something.

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• Event ID 17890 (A significant part... paged out.) with SQL Server 2008

  - by Godeke

  I have a machine that has SQL Server 2008 Standard installed. Periodically (about once an hour) I am getting Event ID 17890 several times in a row. An example: 6:28:54 "A significant part of sql server process memory has been paged out. This may result in a performance degradation. Duration: 0 seconds. Working set (KB): 10652, committed (KB): 628428, memory utilization: 1%%. 6:34:27 "A significant part of sql server process memory has been paged out. This may result in a performance degradation. Duration: 332 seconds. Working set (KB): 169780, committed (KB): 546124, memory utilization: 31%%." 6:38:55 "A significant part of sql server process memory has been paged out. This may result in a performance degradation. Duration: 600 seconds. Working set (KB): 245068, committed (KB): 546124, memory utilization: 44%%." This pattern repeated at 7:26 - 7:37, 8:26 - 8:36, 9:24 - 9:35 and so with the same increasing working set and memory utilization pattern. I don't have any (known) background tasks running at this time. Backups run at 2:00 This subsided from 11:00 at night until it resumed at 4:00 in the morning and has been continuing the intermittent 10 minute glitch periods. As this server has plenty of RAM (the commit charge has peaked at 2,871,564 of 4,194,012 physical) I disabled the paging files after reading several items I dug up searching Google and not finding any of them changing the situation. This pattern I am documented is after removing the paging files, so I'm not even sure where we are paging the SQL process could be going. I also changed the SQL process memory to have a minimum of 500MB and a maximum of 2GB of RAM (as this is a light duty database server serving only a small workgroup). Has anyone encountered this? Prior to disabling the page files this error would cause 5 minutes of disk thrashing that disabled access to the databases, files, IIS webs and so on. Since disabling the page files it just logs strange things, but I'm not seeing a performance drop at least. Any suggestions would be welcome.

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• Joining on NULLs

  - by Dave Ballantyne

  A problem I see on a fairly regular basis is that of dealing with NULL values.  Specifically here, where we are joining two tables on two columns, one of which is ‘optional’ ie is nullable.  So something like this: i.e. Lookup where all the columns are equal, even when NULL.   NULL’s are a tricky thing to initially wrap your mind around.  Statements like “NULL is not equal to NULL and neither is it not not equal to NULL, it’s NULL” can cause a serious brain freeze and leave you a gibbering wreck and needing your mummy. Before we plod on, time to setup some data to demo against. Create table #SourceTable ( Id integer not null, SubId integer null, AnotherCol char(255) not null ) go create unique clustered index idxSourceTable on #SourceTable(id,subID) go with cteNums as ( select top(1000) number from master..spt_values where type ='P' ) insert into #SourceTable select Num1.number,nullif(Num2.number,0),'SomeJunk' from cteNums num1 cross join cteNums num2 go Create table #LookupTable ( Id integer not null, SubID integer null ) go insert into #LookupTable Select top(100) id,subid from #SourceTable where subid is not null order by newid() go insert into #LookupTable Select top(3) id,subid from #SourceTable where subid is null order by newid() If that has run correctly, you will have 1 million rows in #SourceTable and 103 rows in #LookupTable.  We now want to join one to the other. First attempt – Lets just join select * from #SourceTable join #LookupTable on #LookupTable.id = #SourceTable.id and #LookupTable.SubID = #SourceTable.SubID OK, that’s a fail.  We had 100 rows back,  we didn’t correctly account for the 3 rows that have null values.  Remember NULL <> NULL and the join clause specifies SUBID=SUBID, which for those rows is not true. Second attempt – Lets deal with those pesky NULLS select * from #SourceTable join #LookupTable on #LookupTable.id = #SourceTable.id and isnull(#LookupTable.SubID,0) = isnull(#SourceTable.SubID,0) OK, that’s the right result, well done and 99.9% of the time that is where its left. It is a relatively trivial CPU overhead to wrap ISNULL around both columns and compare that result, so no problems.  But, although that’s true, this a relational database we are using here, not a procedural language.  SQL is a declarative language, we are making a request to the engine to get the results we want.  How we ask for them can make a ton of difference. Lets look at the plan for our second attempt, specifically the clustered index seek on the #SourceTable   There are 2 predicates. The ‘seek predicate’ and ‘predicate’.  The ‘seek predicate’ describes how SQLServer has been able to use an Index.  Here, it has been able to navigate the index to resolve where ID=ID.  So far so good, but what about the ‘predicate’ (aka residual probe) ? This is a row-by-row operation.  For each row found in the index matching the Seek Predicate, the leaf level nodes have been scanned and tested using this logical condition.  In this example [Expr1007] is the result of the IsNull operation on #LookupTable and that is tested for equality with the IsNull operation on #SourceTable.  This residual probe is quite a high overhead, if we can express our statement slightly differently to take full advantage of the index and make the test part of the ‘Seek Predicate’. Third attempt – X is null and Y is null So, lets state the query in a slightly manner: select * from #SourceTable join #LookupTable on #LookupTable.id = #SourceTable.id and ( #LookupTable.SubID = #SourceTable.SubID or (#LookupTable.SubID is null and #SourceTable.SubId is null) ) So its slightly wordier and may not be as clear in its intent to the human reader, that is what comments are for, but the key point is that it is now clearer to the query optimizer what our intention is. Let look at the plan for that query, again specifically the index seek operation on #SourceTable No ‘predicate’, just a ‘Seek Predicate’ against the index to resolve both ID and SubID.  A subtle difference that can be easily overlooked.  But has it made a difference to the performance ? Well, yes , a perhaps surprisingly high one. Clever query optimizer well done. If you are using a scalar function on a column, you a pretty much guaranteeing that a residual probe will be used.  By re-wording the query you may well be able to avoid this and use the index completely to resolve lookups. In-terms of performance and scalability your system will be in a much better position if you can.

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• Coherence Data Guarantees for Data Reads - Basic Terminology

  - by jpurdy

  When integrating Coherence into applications, each application has its own set of requirements with respect to data integrity guarantees. Developers often describe these requirements using expressions like "avoiding dirty reads" or "making sure that updates are transactional", but we often find that even in a small group of people, there may be a wide range of opinions as to what these terms mean. This may simply be due to a lack of familiarity, but given that Coherence sits at an intersection of several (mostly) unrelated fields, it may be a matter of conflicting vocabularies (e.g. "consistency" is similar but different in transaction processing versus multi-threaded programming). Since almost all data read consistency issues are related to the concept of concurrency, it is helpful to start with a definition of that, or rather what it means for two operations to be concurrent. Rather than implying that they occur "at the same time", concurrency is a slightly weaker statement -- it simply means that it can't be proven that one event precedes (or follows) the other. As an example, in a Coherence application, if two client members mutate two different cache entries sitting on two different cache servers at roughly the same time, it is likely that one update will precede the other by a significant amount of time (say 0.1ms). However, since there is no guarantee that all four members have their clocks perfectly synchronized, and there is no way to precisely measure the time it takes to send a given message between any two members (that have differing clocks), we consider these to be concurrent operations since we can not (easily) prove otherwise. So this leads to a question that we hear quite frequently: "Are the contents of the near cache always synchronized with the underlying distributed cache?". It's easy to see that if an update on a cache server results in a message being sent to each near cache, and then that near cache being updated that there is a window where the contents are different. However, this is irrelevant, since even if the application reads directly from the distributed cache, another thread update the cache before the read is returned to the application. Even if no other member modifies a cache entry prior to the local near cache entry being updated (and subsequently read), the purpose of reading a cache entry is to do something with the result, usually either displaying for consumption by a human, or by updating the entry based on the current state of the entry. In the former case, it's clear that if the data is updated faster than a human can perceive, then there is no problem (and in many cases this can be relaxed even further). For the latter case, the application must assume that the value might potentially be updated before it has a chance to update it. This almost aways the case with read-only caches, and the solution is the traditional optimistic transaction pattern, which requires the application to explicitly state what assumptions it made about the old value of the cache entry. If the application doesn't want to bother stating those assumptions, it is free to lock the cache entry prior to reading it, ensuring that no other threads will mutate the entry, a pessimistic approach. The optimistic approach relies on what is sometimes called a "fuzzy read". In other words, the application assumes that the read should be correct, but it also acknowledges that it might not be. (I use the qualifier "sometimes" because in some writings, "fuzzy read" indicates the situation where the application actually sees an original value and then later sees an updated value within the same transaction -- however, both definitions are roughly equivalent from an application design perspective). If the read is not correct it is called a "stale read". Going back to the definition of concurrency, it may seem difficult to precisely define a stale read, but the practical way of detecting a stale read is that is will cause the encompassing transaction to roll back if it tries to update that value. The pessimistic approach relies on a "coherent read", a guarantee that the value returned is not only the same as the primary copy of that value, but also that it will remain that way. In most cases this can be used interchangeably with "repeatable read" (though that term has additional implications when used in the context of a database system). In none of cases above is it possible for the application to perform a "dirty read". A dirty read occurs when the application reads a piece of data that was never committed. In practice the only way this can occur is with multi-phase updates such as transactions, where a value may be temporarily update but then withdrawn when a transaction is rolled back. If another thread sees that value prior to the rollback, it is a dirty read. If an application uses optimistic transactions, dirty reads will merely result in a lack of forward progress (this is actually one of the main risks of dirty reads -- they can be chained and potentially cause cascading rollbacks). The concepts of dirty reads, fuzzy reads, stale reads and coherent reads are able to describe the vast majority of requirements that we see in the field. However, the important thing is to define the terms used to define requirements. A quick web search for each of the terms in this article will show multiple meanings, so I've selected what are generally the most common variations, but it never hurts to state each definition explicitly if they are critical to the success of a project (many applications have sufficiently loose requirements that precise terminology can be avoided).

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• Clone a VirtualBox Machine

  I just installed VirtualBox, which I want to try out based on recommendations from peers for running a server from within my Windows 7 x64 OS.  Ive never used VirtualBox, so Im certainly no expert at it, but I did want to share my experience with it thus far.  Specifically, my intention is to create a couple of virtual machines.  One I intend to use as a build server, for which a virtual machine makes sense because I can easily move it around as needed if there are hardware issues (its worth noting my need for setting up a build server at the moment is a result of a disk failure on the old build server).  The other VM I want to set up will act as a proxy server for the issue tracking system were using at Code Project, Axosoft OnTime.  They have a Remote Server application for this purpose, and since the OnTime install is 300 miles away from my location, the Remote Server should speed up my use of the OnTime client by limiting the chattiness with the database (at least, thats the hope). So, I need two VMs, and Im lazy.  I dont want to have to install the OS and such twice.  No problem, it should be simple to clone a virtualbox machine, or clone a virtualbox hard drive, right?  Well unfortunately, if you look at the UI for VirtualBox, theres no such command.  Youre left wondering How do I clone a VirtualBox machine? or the slightly related How do I clone a VirtualBox hard drive? If youve used VirtualPC, then you know that its actually pretty easy to copy and move around those VMs.  Not quite so easy with VirtualBox.  Finding the files is easy, theyre located in your user folder within the .VirtualBox folder (possibly within a HardDisks folder).  The disks have a .vdi extension and will be pretty large if youve installed anything.  The one shown here has just Windows Server 2008 R2 installed on it nothing else. If you copy the .vdi file and rename it, you can use the Virtual Media Manager to view it and you can create a new machine and choose the new drive to attach to.  Unfortunately, if you simply make a copy of the drive, this wont work and youll get an error that says something to the effect of: Cannot register the hard disk PATH with UUID {id goes here} because a hard disk PATH2 with UUID {same id goes here} already exists in the media registry (PATH to XML file). There are command line tools you can use to do this in a way that avoids this error.  Specifically, the c:\Program File\Sun\VirtualBox\VBoxManage.exe program is used for all command line access to VirtualBox, and to copy a virtual disk (.vdi file) you would call something like this: VBoxManage clonehd Disk1.vdi Disk1_Copy.vdi However, in my case this didnt work.  I got basically the same error I showed above, along with some debug information for line 628 of VBoxManageDisk.cpp.  As my main task was not to debug the C++ code used to write VirtualBox, I continued looking for a simple way to clone a virtual drive.  I found it in this blog post. The Secret setvdiuuid Command VBoxManage has a whole bunch of commands you can use with it just pass it /? to see the list.  However, it also has a special command called internalcommands that opens up access to even more commands.  The one thats interesting for us here is the setvdiuuid command.  By calling this command and passing in the file path to your vdi file, it will reset the UUID to a new (random, apparently) UUID.  This then allows the virtual media manager to cope with the file, and lets you set up new machines that reference the newly UUIDd virtual drive.  The full command line would be: VBoxManage internalcommands setvdiuuid MyCopy.vdi The following screenshot shows the error when trying clonehd as well as the successful use of setvdiuuid. Summary Now that I can clone machines easily, its a simple matter to set up base builds of any OS I might need, and then fork from there as needed.  Hopefully the GUI for VirtualBox will be improved to include better support for copying machines/disks, as this is Im sure a very common scenario. Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Trouble with Samba Domain

  - by Arkevius

  I'm having a bit of trouble setting up this Samba domain correctly. I'm getting an Access Denied error when trying to add a Windows XP machine to the domain. I'll go through my scenario in detail, but for those of you wanting a TLDR summary it'll be at the bottom of this post. I have HP Proliant server with Ubuntu 12.04 LTS installed. For this particular environment, I need this server to act as a PDC, file server, and print server. I began by updating and upgrading the packages (of course). Then went to install samba, gnome-desktop, wine, and cpanm. Samba was, of course, for the PDC and file/print services. The GUI was needed because a certain software has to be installed on there that needs a GUI. Wine was needed because the software is Windows-native. And cpanm was for a perl script I have running. For Samba, I went into the smb.conf file and enabled domain logons, changed the workgroup/domain name, the logon script for a per-group basis (netlogon/%g), enabled the netlogon and profiles share, and setup a couple of custom shares for the file service. The printer was added later, and seems to be working just fine. I then restarted the services, and used the net groupmap command to ensure my unix groups were mapped correctly to the Windows groups. After this, I went to a Windows box, and was able to successfully join the domain without a problem. After some fidgeting with the software to get it running on the win boxes from the server (it's a records management system program, which stores it's database files on the server), I went to add another computer to the domain. But now it's saying Access Denied. Before when I had this trouble it was because I forgot to add the group "machines" so Samba could create machine accounts. Thinking this was the case, I manually created the machine account to test this theory. However, it would still give me an Access Denied error. That must mean it has something to do with permissions now, correct? I've been fighting with this server for the past two weeks. If it's not one thing that;s wrong, then it's something else completely different. This would be the third time I've actually reinstalled everything to start over. I'll post snippets of my system settings below. If anything else is needed, just say the word and I'll gather up the info. The unix group 'domadmin' is the Domain Admins group. Samba Administrator account administrator:x:1000:1000:Administrator,,,:/home/administrator:/bin/bash Adminstrator's groups administrator adm cdrom sudo dip plugdev lpadmin sambashare domadmin crimestar Samba's Configuration FIle (a snippet anyways) [global] workgroup = CITYPD server string = BPDServer dns proxy = no log file = /var/log/samba/log.%m max log size = 1000 syslog = 0 panic action = /usr/share/samba/panic-action %d security = user encrypt passwords = true passdb backend = tdbsam obey pam restrictions = yes unix password sync = yes passwd program = /usr/bin/passwd %u passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* . pam password change = yes map to guest = bad user domain logons = yes logon path = \\%L\srv\samba\profiles\%U logon script = logon.bat add machine script = /usr/sbin/useradd -g machines -c "%u machine account" -d /var/lib/samba -s /bin/false %u domain master = yes usershare allow guests = yes [netlogon] comment = Network Logon Service path = /srv/samba/netlogon/%g guest ok = yes read only = yes browseable = no [profiles] comment = All Printers browseable = no path = /var/spool/samba printable = yes guest ok = no read only = yes create mask = 0700 [print$] comment = Printer Drivers path = /var/lib/samba/printers browseable = yes read only = yes guest ok = no write list = root, @lpadmin [crimestar] comment = "Crimestar DB" path = /srv/crimestar/db valid users = @domadmin, @crimestar admin users = administrator writeable = yes guest ok = no browseable = no create mask = 0666 directory mask = 0777 [crimestarfiles] path = /home/administrator/.wine/drive_c/crimestar admin users = administrator browseable = yes ls -la on /srv/samba/profiles drwxrwxrwx 2 root machines 4096 Nov 21 15:27 . drwxr-xr-x 4 root root 4096 Nov 21 15:28 .. ls -la on /srv/samba/netlogon drwxr-xr-x 6 root root 4096 Nov 21 15:30 . drwxr-xr-x 4 root root 4096 Nov 21 15:28 .. drwxr-xr-x 2 root root 4096 Nov 21 15:30 crimestar drwxr-xr-x 2 root root 4096 Nov 21 18:13 domadmin drwxr-xr-x 3 root root 4096 Nov 21 15:30 guests drwxr-xr-x 2 root root 4096 Nov 21 15:29 users GrouMap list Domain Users (S-1-5-21-2978508755-2341913247-928297747-513) -> users Domain Admins (S-1-5-21-2978508755-2341913247-928297747-512) -> domadmin Domain Guests (S-1-5-21-2978508755-2341913247-928297747-514) -> nogroup TLDR I'm getting an Access Denied error message while trying to join a windows box to a samba domain, even after I successfully joined another computer without a problem. System settings / files are quoted above. Anyone have any ideas or suggestions?

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• World Backup Day

  - by red(at)work

  Here at Red Gate Towers, the SQL Backup development team have been hunkered down in their shed for the last few months, with the toolbox, blowtorch and chamois leather out, upgrading SQL Backup. When we started, autumn leaves were falling. Now we're about to finish, spring flowers are budding. If not quite a gleaming new machine, at the very least a familiar, reliable engine with some shiny new bits on it will trundle magnificently out of the workshop. One of the interesting things I've noticed about working on software development teams is that the team is together for so long 'implementing' stuff - designing, coding, testing, fixing bugs and so on - that you occasionally forget why you're doing what you're doing. Doubt creeps in. It feels like a long time since we launched this project in a fanfare of optimism and enthusiasm, and all that clarity of purpose and mission "yee-haw" has dissipated with the daily pressures of development. Every now and again, we look up from our bunker and notice all those thousands of users out there, with their different configurations and working practices and each with their own set of problems and requirements, and we ask ourselves "does anyone care about what we're doing?" Has the world moved on while we've been busy? Could we have been doing something more useful with the time and talent of all these excellent people we've assembled? In truth, you can research and test and validate all you like, but you never really know if you've done the right thing (or at least, something valuable for some users) until you release. All projects suffer this insecurity. If they don't, maybe you're not worrying enough about what you're building. The two enemies of software development are certainty and complacency. Oh, and of course, rival teams with Nerf guns. The goal of SQL Backup 7 is to make it so easy to schedule regular restores of your backups that you have no excuse not to. Why schedule a restore? Because your data is not as good as your last backup. It's only as good as your last successful restore. If you're not checking your backups by restoring them and running an integrity check on the database, you're only doing half the job. It seems that most DBAs know that this is best practice, but it can be tricky and time-consuming to set up, so it's one of those tasks that can get forgotten in the midst all the other demands on their time. Sometimes, they're just too busy firefighting. But if it was simple to do? That was our inspiration for SQL Backup 7. So it was heartening to read Brent Ozar's blog post the other day about World Backup Day. To be honest, I'd never heard of World Backup Day (Talk Like a Pirate Day, yes, but not this one); however, its emphasis on not just backing up your data but checking the validity of those backups was exactly the same message we had in mind when building SQL Backup 7. It's printed on a piece of A3 above our planning board - "Make backup verification so easy to do that no DBA has an excuse for not doing it" It's the missing piece that completes the puzzle. Simple idea, great concept, useful feature, but, as it turned out, far from straightforward to implement. The problem is the future. As Marty McFly discovered over the course of three movies, the future is uncertain and hard to predict - so when you are scheduling a restore to take place an hour, day, week or month after the backup, there are all kinds of questions that you wouldn't normally have to consider. Where will this backup live? Will it even exist at the time? Will it be split into multiple files? What will the file names be? Will it be encrypted? What files should it be restored to? SQL Backup needs to know what to expect at the time the restore job is actually run. Of course, a DBA will know the answer to all these questions, but to deliver the whole point of version 7, we wanted to make it easy for them to input that information into SQL Backup. We think we've done that. When you create your scheduled backup job, there is now an option to create a "reminder" to follow it up with a scheduled restore to verify the resulting backups. Actually, it's much more than a reminder, as it stores all the relevant data so you can click it and pre-populate the wizard with all the right settings to set up your verification restores. Simple. But, what do you think? We'd love you to try it. Post by Brian Harris

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• Cloud Computing Forces Better Design Practices

  - by Herve Roggero

  Is cloud computing simply different than on premise development, or is cloud computing actually forcing you to create better applications than you normally would? In other words, is cloud computing merely imposing different design principles, or forcing better design principles?  A little while back I got into a discussion with a developer in which I was arguing that cloud computing, and specifically Windows Azure in his case, was forcing developers to adopt better design principles. His opinion was that cloud computing was not yielding better systems; just different systems. In this blog, I will argue that cloud computing does force developers to use better design practices, and hence better applications. So the first thing to define, of course, is the word “better”, in the context of application development. Looking at a few definitions online, better means “superior quality”. As it relates to this discussion then, I stipulate that cloud computing can yield higher quality applications in terms of scalability, everything else being equal. Before going further I need to also outline the difference between performance and scalability. Performance and scalability are two related concepts, but they don’t mean the same thing. Scalability is the measure of system performance given various loads. So when developers design for performance, they usually give higher priority to a given load and tend to optimize for the given load. When developers design for scalability, the actual performance at a given load is not as important; the ability to ensure reasonable performance regardless of the load becomes the objective. This can lead to very different design choices. For example, if your objective is to obtains the fastest response time possible for a service you are building, you may choose the implement a TCP connection that never closes until the client chooses to close the connection (in other words, a tightly coupled service from a connectivity standpoint), and on which a connection session is established for faster processing on the next request (like SQL Server or other database systems for example). If you objective is to scale, you may implement a service that answers to requests without keeping session state, so that server resources are released as quickly as possible, like a REST service for example. This alternate design would likely have a slower response time than the TCP service for any given load, but would continue to function at very large loads because of its inherently loosely coupled design. An example of a REST service is the NO-SQL implementation in the Microsoft cloud called Azure Tables. Now, back to cloud computing… Cloud computing is designed to help you scale your applications, specifically when you use Platform as a Service (PaaS) offerings. However it’s not automatic. You can design a tightly-coupled TCP service as discussed above, and as you can imagine, it probably won’t scale even if you place the service in the cloud because it isn’t using a connection pattern that will allow it to scale [note: I am not implying that all TCP systems do not scale; I am just illustrating the scalability concepts with an imaginary TCP service that isn’t designed to scale for the purpose of this discussion]. The other service, using REST, will have a better chance to scale because, by design, it minimizes resource consumption for individual requests and doesn’t tie a client connection to a specific endpoint (which means you can easily deploy this service to hundreds of machines without much trouble, as long as your pockets are deep enough). The TCP and REST services discussed above are both valid designs; the TCP service is faster and the REST service scales better. So is it fair to say that one service is fundamentally better than the other? No; not unless you need to scale. And if you don’t need to scale, then you don’t need the cloud in the first place. However, it is interesting to note that if you do need to scale, then a loosely coupled system becomes a better design because it can almost always scale better than a tightly-coupled system. And because most applications grow overtime, with an increasing user base, new functional requirements, increased data and so forth, most applications eventually do need to scale. So in my humble opinion, I conclude that a loosely coupled system is not just different than a tightly coupled system; it is a better design, because it will stand the test of time. And in my book, if a system stands the test of time better than another, it is of superior quality. Because cloud computing demands loosely coupled systems so that its underlying service architecture can be leveraged, developers ultimately have no choice but to design loosely coupled systems for the cloud. And because loosely coupled systems are better… … the cloud forces better design practices. My 2 cents.

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• Developing Schema Compare for Oracle (Part 4): Script Configuration

  - by Simon Cooper

  If you've had a chance to play around with the Schema Compare for Oracle beta, you may have come across this screen in the synchronization wizard: This screen is one of the few screens that, along with the project configuration form, doesn't come from SQL Compare. This screen was designed to solve a couple of issues that, although aren't specific to Oracle, are much more of a problem than on SQL Server: Datatype conversions and NOT NULL columns. 1. Datatype conversions SQL Server is generally quite forgiving when it comes to datatype conversions using ALTER TABLE. For example, you can convert from a VARCHAR to INT using ALTER TABLE as long as all the character values are parsable as integers. Oracle, on the other hand, only allows ALTER TABLE conversions that don't change the internal data format. Essentially, every change that requires an actual datatype conversion has to be done using a rebuild with a conversion function. That's OK, as we can simply hard-code the various conversion functions for the valid datatype conversions and insert those into the rebuild SELECT list. However, as there always is with Oracle, there's a catch. Have a look at the NUMTODSINTERVAL function. As well as specifying the value (or column) to convert, you have to specify an interval_unit, which tells oracle how to interpret the input number. We can't hardcode a default for this parameter, as it is entirely dependent on the user's data context! So, in order to convert NUMBER to INTERVAL DAY TO SECOND/INTERVAL YEAR TO MONTH, we need to have feedback from the user as to what to put in this parameter while we're generating the sync script - this requires a new step in the engine action/script generation to insert these values into the script, as well as new UI to allow the user to specify these values in a sensible fashion. In implementing the engine and UI infrastructure to allow this it made much more sense to implement it for any rebuild datatype conversion, not just NUMBER to INTERVALs. For conversions which we can do, we pre-fill the 'value' box with the appropriate function from the documentation. The user can also type in arbitary SQL expressions, which allows the user to specify optional format parameters for the relevant conversion functions, or indeed call their own functions to convert between values that don't have a built-in conversion defined. As the value gets inserted as-is into the rebuild SELECT list, any expression that is valid in that context can be specified as the conversion value. 2. NOT NULL columns Another problem that is solved by the new step in the sync wizard is adding a NOT NULL column to a table. If the table contains data (as most database tables do), you can't just add a NOT NULL column, as Oracle doesn't know what value to put in the new column for existing rows - the DDL statement will fail. There are actually 3 separate scenarios for this problem that have separate solutions within the engine: Adding a NOT NULL column to a table without a rebuild Here, the workaround is to add a column default with an appropriate value to the column you're adding: ALTER TABLE tbl1 ADD newcol NUMBER DEFAULT <value> NOT NULL; Note, however, there is something to bear in mind about this solution; once specified on a column, a default cannot be removed. To 'remove' a default from a column you change it to have a default of NULL, hence there's code in the engine to treat a NULL default the same as no default at all. Adding a NOT NULL column to a table, where a separate change forced a table rebuild Fortunately, in this case, a column default is not required - we can simply insert the default value into the rebuild SELECT clause. Changing an existing NULL to a NOT NULL column To implement this, we run an UPDATE command before the ALTER TABLE to change all the NULLs in the column to the required default value. For all three, we need some way of allowing the user to specify a default value to use instead of NULL; as this is essentially the same problem as datatype conversion (inserting values into the sync script), we can re-use the UI and engine implementation of datatype conversion values. We also provide the option to alter the new column to allow NULLs, or to ignore the problem completely. Note that there is the same (long-running) problem in SQL Compare, but it is much more of an issue in Oracle as you cannot easily roll back executed DDL statements if the script fails at some point during execution. Furthermore, the engine of SQL Compare is far less conducive to inserting user-supplied values into the generated script. As we're writing the Schema Compare engine from scratch, we used what we learnt from the SQL Compare engine and designed it to be far more modular, which makes inserting procedures like this much easier.

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• Processing Text and Binary (Blob, ArrayBuffer, ArrayBufferView) Payload in WebSocket - (TOTD #185)

  - by arungupta

  The WebSocket API defines different send(xxx) methods that can be used to send text and binary data. This Tip Of The Day (TOTD) will show how to send and receive text and binary data using WebSocket. TOTD #183 explains how to get started with a WebSocket endpoint using GlassFish 4. A simple endpoint from that blog looks like: @WebSocketEndpoint("/endpoint") public class MyEndpoint { public void receiveTextMessage(String message) { . . . } } A message with the first parameter of the type String is invoked when a text payload is received. The payload of the incoming WebSocket frame is mapped to this first parameter. An optional second parameter, Session, can be specified to map to the "other end" of this conversation. For example: public void receiveTextMessage(String message, Session session) {     . . . } The return type is void and that means no response is returned to the client that invoked this endpoint. A response may be returned to the client in two different ways. First, set the return type to the expected type, such as: public String receiveTextMessage(String message) { String response = . . . . . . return response; } In this case a text payload is returned back to the invoking endpoint. The second way to send a response back is to use the mapped session to send response using one of the sendXXX methods in Session, when and if needed. public void receiveTextMessage(String message, Session session) {     . . .     RemoteEndpoint remote = session.getRemote();     remote.sendString(...);     . . .     remote.sendString(...);    . . .    remote.sendString(...); } This shows how duplex and asynchronous communication between the two endpoints can be achieved. This can be used to define different message exchange patterns between the client and server. The WebSocket client can send the message as: websocket.send(myTextField.value); where myTextField is a text field in the web page. Binary payload in the incoming WebSocket frame can be received if ByteBuffer is used as the first parameter of the method signature. The endpoint method signature in that case would look like: public void receiveBinaryMessage(ByteBuffer message) {     . . . } From the client side, the binary data can be sent using Blob, ArrayBuffer, and ArrayBufferView. Blob is a just raw data and the actual interpretation is left to the application. ArrayBuffer and ArrayBufferView are defined in the TypedArray specification and are designed to send binary data using WebSocket. In short, ArrayBuffer is a fixed-length binary buffer with no format and no mechanism for accessing its contents. These buffers are manipulated using one of the views defined by one of the subclasses of ArrayBufferView listed below: Int8Array (signed 8-bit integer or char) Uint8Array (unsigned 8-bit integer or unsigned char) Int16Array (signed 16-bit integer or short) Uint16Array (unsigned 16-bit integer or unsigned short) Int32Array (signed 32-bit integer or int) Uint32Array (unsigned 16-bit integer or unsigned int) Float32Array (signed 32-bit float or float) Float64Array (signed 64-bit float or double) WebSocket can send binary data using ArrayBuffer with a view defined by a subclass of ArrayBufferView or a subclass of ArrayBufferView itself. The WebSocket client can send the message using Blob as: blob = new Blob([myField2.value]);websocket.send(blob); where myField2 is a text field in the web page. The WebSocket client can send the message using ArrayBuffer as: var buffer = new ArrayBuffer(10);var bytes = new Uint8Array(buffer);for (var i=0; i<bytes.length; i++) { bytes[i] = i;}websocket.send(buffer); A concrete implementation of receiving the binary message may look like: @WebSocketMessagepublic void echoBinary(ByteBuffer data, Session session) throws IOException {    System.out.println("echoBinary: " + data);    for (byte b : data.array()) {        System.out.print(b);    }    session.getRemote().sendBytes(data);} This method is just printing the binary data for verification but you may actually be storing it in a database or converting to an image or something more meaningful. Be aware of TYRUS-51 if you are trying to send binary data from server to client using method return type. Here are some references for you: JSR 356: Java API for WebSocket - Specification (Early Draft) and Implementation (already integrated in GlassFish 4 promoted builds) TOTD #183 - Getting Started with WebSocket in GlassFish TOTD #184 - Logging WebSocket Frames using Chrome Developer Tools, Net-internals and Wireshark Subsequent blogs will discuss the following topics (not necessary in that order) ... Error handling Custom payloads using encoder/decoder Interface-driven WebSocket endpoint Java client API Client and Server configuration Security Subprotocols Extensions Other topics from the API

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• 20GB+ worth of emails in my /home what is a better solution for that?

  - by Skinkie

  My email storage requirements are outgrowing anything reasonable with respect to local mail storage. As we speak 99% of my home partition is filled with personal mail in Thunderbirds mail dirs. Needless to say, this is just painful, badly searchable and as history has proven me that backups work, but Thunderbird is capable of loosing a lot of mail very easily. Currently I have an remote IMAPS server (Dovecot) running for my daily mail, accessible from anywhere, which from my own practice works efficiently up to about 1000 emails. Then some archive directories should be used to move mail around. I have been looking into DBMail, but I wonder if I make my case worse or better which such solution. None of the supported database employ string deduplication or string compression out of the box, so is this going to help me with 20GB+ mail? What about falling back to a plain old IMAP server? A filesystem like ZFS would support stuff like GZIP transparently, which could help. Could someone share their thoughts? The 20GB mostly consists of mailinglists, and normal mail. Not things like attachments. To add some clarifications; As we speak, my mail is not server side indexed at all - only my new mail arrives at a remote IMAP server. It is all local storage from former POP3 accounts, local mirrored Gmail and IMAP accounts. In my perspective it is not Thunderbird that sucks, its fileformat that sucks. Regarding the 1000 mails. On the road I am using Alpine and MobileMail, quite happy with both of them, but some management is required to actually manage the mail. Sieve helps a lot with that, but browing through 10.000 e-mails is not fun, especially not on a mobile client. I am quite happy with Dovecot, never had any issues with it. I just wonder if this is the way to go. Or if there are any other better solutions. What my question is: what is the best practice solution that allows 20GB+ mails and is -on demand remotely accessible, easy to backup and archive worthy. It doesn't need to be available 24x7. The final approach I took was installing a local IMAP server (Dovecot), configured it for being my archive, using the following guide: http://en.gentoo-wiki.com/wiki/Dovecot/InstallThunderbird

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• Is software support an option for your career?

  - by Maria Sandu

  Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 If you have a technical background, why should you choose a career in support? We have invited Serban to answer these questions and to give us an overview of one of the biggest technical teams in Oracle Romania. He’s been with Oracle for 7 years leading the local PeopleSoft Financials & Supply Chain Support team. Back in 2013 Serban started building a new support team in Romania – Fusion HCM. His current focus is building a strong support team for Fusion HCM, latest solution for Business HR Professionals from Oracle. The solution is offered both on Premise (customer site installation) but more important as a Cloud offering – SaaS.  So, why should a technical person choose Software Support over other technical areas?  “I think it is mainly because of the high level of technical skills required to provide the best technical solutions to our customers. Oracle Software Support covers complex solutions going from Database or Middleware to a vast area of business applications (basically covering any needs that a large enterprise may have). Working with such software requires very strong skills both technical and functional for the different areas, going from Finance, Supply Chain Management, Manufacturing, Sales to other very specific business processes. Our customers are large enterprises that already have a support layer inside their organization and therefore the Oracle Technical Support Engineers are working with highly specialized staff (DBA’s, System/Application Admins, Implementation Consultants). This is a very important aspect for our engineers because they need to be highly skilled to match our customer’s specialist’s expectations”.  What’s the career path in your team? “Technical Analysts joining our teams have a clear growth path. The main focus is to become a master of the product they will support. I think one need 1 or 2 years to reach a good level of understanding the product and delivering optimal solutions because of the complexity of our products. At a later stage, engineers can choose their professional development areas based on the business needs and preferences and then further grow towards as technical expert or a management role. We have analysts that have more than 15 years of technical expertise and they still learn and grow in technical area. Important fact is, due to the expansion of the Romanian Software support center, there are various management opportunities. So, if you want to leverage your experience and if you want to have people management responsibilities Oracle Software Support is the place to be!”  Our last question to Serban was about the benefits of being part of Oracle Software Support. Here is what he said: “We believe that Oracle delivers “State of the art” Support level to our customers. This is not possible without high investment in our staff. We commit from the start to support any technical analyst that joins us (being junior or very senior) with any training needs they have for their job. We have various technical trainings as well as soft-skills trainings required for a customer facing professional to be successful in his role. Last but not least, we’re aiming to make Oracle Romania SW Support a global center of excellence which means we’re investing a lot in our employees.”  If you’re looking for a job where you can combine your strong technical skills with customer interaction Oracle Software Support is the place to be! Send us your CV at [email protected]. /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

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• Exchange IMAP4 connector - Error Event ID 2006

  - by MikeB

  A couple of users in my organisation use IMAP4 to connect to Exchange 2007 (Update rollup 9 applied) because they prefer Thunderbird / Postbox clients. One of the users is generating errors in the Application Log as follows: An exception Microsoft.Exchange.Data.Storage.ConversionFailedException occurred while converting message Imap4Message 1523, user "*******", folder *********, subject: "******", date: "*******" into MIME format. Microsoft.Exchange.Data.Storage.ConversionFailedException: Message content has become corrupted. ---> System.ArgumentException: Value should be a valid content type in the form 'token/token' Parameter name: value at Microsoft.Exchange.Data.Mime.ContentTypeHeader.set_Value(String value) at Microsoft.Exchange.Data.Storage.MimeStreamWriter.WriteHeader(HeaderId type, String data) at Microsoft.Exchange.Data.Storage.ItemToMimeConverter.WriteMimeStreamAttachment(StreamAttachmentBase attachment, MimeFlags flags) --- End of inner exception stack trace --- at Microsoft.Exchange.Data.Storage.ItemToMimeConverter.WriteMimeStreamAttachment(StreamAttachmentBase attachment, MimeFlags flags) at Microsoft.Exchange.Data.Storage.ItemToMimeConverter.WriteMimeAttachment(MimePartInfo part, MimeFlags flags) at Microsoft.Exchange.Data.Storage.ItemToMimeConverter.WriteMimePart(MimePartInfo part, MimeFlags mimeFlags) at Microsoft.Exchange.Data.Storage.ItemToMimeConverter.WriteMimeParts(List`1 parts, MimeFlags mimeFlags) at Microsoft.Exchange.Data.Storage.ItemToMimeConverter.WriteMimePart(MimePartInfo part, MimeFlags mimeFlags) at Microsoft.Exchange.Data.Storage.ImapItemConverter.<>c__DisplayClass2.<WriteMimePart>b__0() at Microsoft.Exchange.Data.Storage.ConvertUtils.CallCts(Trace tracer, String methodName, String exceptionString, CtsCall ctsCall) at Microsoft.Exchange.Data.Storage.ImapItemConverter.WriteMimePart(ItemToMimeConverter converter, MimeStreamWriter writer, OutboundConversionOptions options, MimePartInfo partInfo, MimeFlags conversionFlags) at Microsoft.Exchange.Data.Storage.ImapItemConverter.GetBody(Stream outStream) at Microsoft.Exchange.Data.Storage.ImapItemConverter.GetBody(Stream outStream, UInt32[] indices) From my reading around it seems that the suggestion is to ask users to log in to Outlook / OWA and view the messages there. However, having logged in as the users myself, the messages cannot be found either through searching or by browsing the folder detailed in the log entry. The server returns the following error to the client: "The message could not be retrieved using the IMAP4 protocol. The message has not been deleted and may be accessible using either Microsoft Outlook or Microsoft Office Outlook Web Access. You can also try contacting the original sender of the message to find out about the contents of the message. Retrieval of this message will be retried when the server is updated with a fix that addresses the problem." Messages were transferred in to Exchange by copying them from the old Apple Xserve, accessed using IMAP. So my question, finally: 1. Is there any way to get the IMAP Exchange connector to rebuild its cache of messages since it doesn't seem to be pulling them directly from the MAPI store? 2. Alternatively, if there is no database, any ideas on why these messages don't appear in Outlook or OWA would be gratefully received. Many thanks, Mike

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• Is there a Distributed SAN/Storage System out there?

  - by Joel Coel

  Like many other places, we ask our users not to save files to their local machines. Instead, we encourage that they be put on a file server so that others (with appropriate permissions) can use them and that the files are backed up properly. The result of this is that most users have large hard drives that are sitting mainly empty. It's 2010 now. Surely there is a system out there that lets you turn that empty space into a virtual SAN or document library? What I envision is a client program that is pushed out to users' PCs that coordinates with a central server. The server looks to users just like a normal file server, but instead of keeping entire file contents it merely keeps a record of where those files can be found among various user PCs. It then coordinates with the right clients to serve up file requests. The client software would be able to respond to such requests directly, as well as be smart enough to cache recent files locally. For redundancy the server could make sure files are copied to multiple PCs, perhaps allowing you to define groups in different locations so that an instance of the entire repository lives in each group to protect against a disaster in one building taking down everything else. Obviously you wouldn't point your database server here, but for simpler things I see several advantages: Files can often be transferred from a nearer machine. Disk space grows automatically as your company does. Should ultimately be cheaper, as you don't need to keep a separate set of disks I can see a few downsides as well: Occasional degradation of user pc performance, if the machine has to serve or accept a large file transfer during a busy period. Writes have to be propogated around the network several times (though I suspect this isn't really much of a problem, as reading happens in most places more than writing) Still need a way to send a complete copy of the data offsite occasionally, and this would make it very hard to do differentials Think of this like a cloud storage system that lives entirely within your corporate LAN and makes use of your existing user equipment. Our old main file server is due for retirement in about 2 years, and I'm looking into replacing it with a small SAN. I'm thinking something like this would be a better fit. As a school, we have a couple computer labs I can leave running that would be perfect for adding a little extra redundancy to the system. Unfortunately, the closest thing I can find is Dienst, and it's just a paper that dates back to 1994. Am I just using the wrong buzzwords in my searches, or does this really not exist? If not, is there a big downside that I'm missing?

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• How to Deploy an ASP.NET Web API- and Browser-based Application to a Production Environment

  - by user69508

  (Please forgive if this is posted in an incorrect forum. We didn’t know exactly where to post it.) We have an ASP.NET Web API single page application - a browser-based app running in IIS to serve up HTML5/CSS3/JavaScript, which talks to the ASP.NET Web API endpoint only to access a database and transfer JSON data. Everything is working great in our development environment - that is, we have one Visual Studio solution with an ASP.NET Web API project and two class library projects for data access. While development and testing on development boxes, using IIS Express to a localhost:port to run the site and access the Web API, everything is fine. Now we need to move it to a production environment (and we’re having problems - or just not understanding what needs to be done). The production environment is all internal (nothing will be exposed on the public Internet). There are two domains. One domain, the corporate domain, is where all users login normally. The other domain, the process domain, contains the SQL Server instance that our app and Web API will need to access. The IT staff wants to put a DMZ between the two domains to house the IIS app and shield the users on the corporate domain from having access into the process domain directly. So, I guess what they want is: corp domain (end users) <– firewall (open port 80) <– DMZ (web server running IIS) <– firewall (open port 80 or 1433????) <– process domain (IIS for Web API and SQL Server) We’re developers and don’t really understand all the networking aspects, so we’re wondering how to deploy our browser/Web API application in this scenario. Do we need to break up our application so that all the client code (HTML5/CSS3/JavaScript/images/etc.) is on the IIS server in the DMZ, while the Web API gets installed on the server in the process domain? Or, does the entire app (client code and Web API) stay together on the IIS server in the DMZ, which then somehow accesses the SQL Server instance to get data? From the IIS server and app in the DMZ, would you simply access the Web API on the server in the process domain by going to "http://server/appname/api/getitmes"? In the second firewall between the DMZ and the process domain, would you have to open port 1433 or just port 80 since the Web API is a HTTP endpoint? Or, is there some better way of deployment (i.e., how ASP.NET Web API single page applications written all in HTML5 and JavaScript supposed to be deployed to production environments?)? I’m sure there are other questions, but we’ll start with these. Thanks!!! (Note: the servers are Win2k8 R2, SQL Server 2k8 R2, and IIS 7.5.)

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• How should we serve files in a small bioinformatics cluster?

  - by cespinoza

  We have a small cluster of six ubuntu servers. We run bioinformatics analyses on these clusters. Each analysis takes about 24 hours to complete, each core i7 server can handle 2 at a time, takes as input about 5GB data and outputs about 10-25GB of data. We run dozens of these a week. The software is a hodgepodge of custom perl scripts and 3rd party sequence alignment software written in C/C++. Currently, files are served from two of the compute nodes (yes, we're using compute nodes as file servers)-- each node has 5 1TB sata drives mounted separately (no raid) and is pooled via glusterfs 2.0.1. They each have as 3 bonded intel ethernet pci gigabit ethernet cards, attached to a d-link DGS-1224T switch ($300 24 port consumer-level). We are not currently using jumbo frames (not sure why, actually). The two file-serving compute nodes are then mirrored via glusterfs. Each of the four other nodes mounts the files via glusterfs. The files are all large (4gb+), and are stored as bare files (no database/etc) if that matters. As you can imagine, this is a bit of a mess that grew organically without forethought and we want to improve it now that we're running out of space. Our analyses are I/O intensive and it is a bottle neck-- we're only getting 140mB/sec between the two fileservers, maybe 50mb/sec from the clients (which only have single NICs). We have a flexible budget which I can probably get up $5k or so. How should we spend our budget? We need at least 10TB of storage fast enough to serve all nodes. How fast/big does the cpu/memory of such a file server have to be? Should we use NFS, ATA over Ethernet, iSCSI, Glusterfs, or something else? Should we buy two or more servers and create some sort of storage cluster, or is 1 server enough for such a small number of nodes? Should we invest in faster NICs (say, PCI-express cards with multiple connectors)? The switch? Should we use raid, if so, hardware or software? and which raid (5, 6, 10, etc)? Any ideas appreciated. We're biologists, not IT gurus.

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• What's New in Oracle VM VirtualBox 4.2?

  - by Fat Bloke

  A year is a long time in the IT industry. Since the last VirtualBox feature release, which was a little over a year ago, we've seen: new releases of cool new operating systems, such as Windows 8, ChromeOS, and Mountain Lion; we've seen a myriad of new Linux releases from big Enterprise class distributions like Oracle 6.3, to accessible desktop distros like Ubuntu 12.04 and Fedora 17; and we've also seen the spec of a typical PC or laptop double in power. All of these events have influenced our new VirtualBox version which we're releasing today. Here's how... Powerful hosts  One of the trends we've seen is that as the average host platform becomes more powerful, our users are consistently running more and more vm's. Some of our users have large libraries of vm's of various vintages, whilst others have groups of vm's that are run together as an assembly of the various tiers in a multi-tiered software solution, for example, a database tier, middleware tier, and front-ends.  So we're pleased to unveil a more powerful VirtualBox Manager to address the needs of these users: VM Groups Groups allow you to organize your VM library in a sensible way, e.g.  by platform type, by project, by version, by whatever. To create groups you can drag one VM onto another or select one or more VM's and choose Machine...Group from the menu bar. You can expand and collapse groups to save screen real estate, and you can Enter and Leave a group (think iPad navigation here) by using the right and left arrow keys when groups are selected. But groups are more than passive folders, because you can now also perform operations on groups, rather than all the individual VMs. So if you have a multi-tiered solution you can start the whole stack up with just one click. Autostart Many VirtualBox users run dedicated services in their VMs, for example, running a Wiki. With these types of VM workloads, you really want the VM start up when the host machine boots up. So with 4.2 we've introduced a cross-platform Auto-start mechanism to allow you to treat VMs as host services. Headless VM Launching With VM's such as web servers, wikis, and other types of server-class workloads, the Console of the VM is pretty much redundant. For some time now VirtualBox has offered a separate launch mechanism for these VM's, namely the command-line interface commands VBoxHeadless or VBoxManage startvm ... --type headless commands. But with 4.2 we also allow you launch headless VMs from the Manager. Simply hold down Shift when launching the VM from the Manager.  It's that easy. But how do you stop a headless VM? Well, with 4.2 we allow you to Close the VM from the Manager. (BTW best to use the ACPI Shutdown method which allows the guest VM to close down gracefully.) Easy VM Creation For our expert users, the  New VM Wizard was a little tiresome, so now there's a faster 2-click VM creation mode. Just Hide the description when creating a new VM. Powerful VMs  As the hosts have become more powerful, so are the guests that are running inside them. Here are some of the 4.2 features to accommodate them: Virtual Network Interface Cards  With 4.2, it's now possible to create VMs with up to 36 NICs, when using the ICH9 chipset emulation. But with great power comes great responsibility (didn't Obi-Wan say something similar?), and so we have also introduced bandwidth limiting to prevent a rogue VM stealing the whole pipe. VLAN tagging Some of our users leverage VLANs extensively so we've enhanced the E1000 NICs to support this.  Processor Performance If you are running a CPU which supports Nested Paging (aka EPT in the Intel world) such as most of the Core i5 and i7 CPUs, or are running an AMD Bulldozer or later, you should see some performance improvements from our work with these processors. And while we're talking Processors, we've added support for some of the more modern VIA CPUs too. Powerful Automation Because VirtualBox runs atop a fully blown operating system, it makes sense to leverage the capabilities of the host to run scripts that can drive the guest VMs. Guest Automation was introduced in a prior release but with 4.2 we've revamped the APIs to allow a richer and more powerful set of operations to be executed by the guest. Check out the IGuest APIs in the VirtualBox Programming Guide and Reference (SDK). Powerful Platforms  All the hardcore engineering that has gone into 4.2 has been done for a purpose and that is to deliver a fast and powerful engine that can run almost any x86 OS because of the integrity of the virtualization. So we're pleased to add support for these platforms: Mac OS X "Mountain Lion"  Windows 8 Windows Server 2012 Ubuntu 12.04 (“Precise Pangolin”) Fedora 17 Oracle Linux 6.3  Here's the proof: We don't have time to go into the myriad of smaller improvements such as support for burning audio CDs from a guest, bi-directional clipboard control,  drag-and-drop of files into Linux guests, etc. so we'll leave that as an exercise for the user as soon as you've downloaded from the Oracle or community site and taken a peek at the User Guide. So all in all, a pretty solid release, one that we hope you'll enjoy discovering. - FB 

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• Exadata?????????INSERT?UPDATE

  - by Liu Maclean(???)

  Hybrid Columnar Compression??????Exadata?????????????,??????????(advanced compression)??,Hybrid columnar compression (HCC) ???Exadata????????HCC???????????CU(compression unit?????),??CU??????????,?????????????????????????,???CU????block??????????????? ???????INSERT/UPDATE??,??????????????,????UPDATE/INSERT???HCC?????????????????? hybrid columnar compression???????????????(bulk initial load)??,??????(direct load)??ALTER TABLE MOVE, IMPDP???????(append INSERT),??HCC??????????????????????? ???????????????????,?????????CU????????? ??????????????HCC?????????????for OLTP?????? ????????: SQL*Plus: Release 11.2.0.2.0 Production on Wed Sep 12 06:14:53 2012 Copyright (c) 1982, 2010, Oracle. All rights reserved. Connected to: Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - Production With the Partitioning, Automatic Storage Management, OLAP, Data Mining and Real Application Testing options SQL> grant dba to scott; Grant succeeded. SQL> conn scott/oracle Connected. SQL> SQL> create table hcc_maclean tablespace users compress for query high as select * from dba_objects; Table created. 1* select rowid,owner,object_name,dbms_rowid.rowid_block_number(rowid) from hcc_maclean where owner='MACLEAN' SQL> / ROWID OWNER OBJECT_NAME DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID) ------------------------------ ------------------------------ -------------------- ------------------------------------ AAAThuAAEAAAHTJAOI MACLEAN SALES 29897 AAAThuAAEAAAHTJAOJ MACLEAN MYCUSTOMERS 29897 AAAThuAAEAAAHTJAOK MACLEAN MYCUST_ARCHIVE 29897 AAAThuAAEAAAHTJAOL MACLEAN MYCUST_QUERY 29897 AAAThuAAEAAAHTJAOh MACLEAN COMPRESS_QUERY 29897 AAAThuAAEAAAHTJAOi MACLEAN UNCOMPRESS 29897 AAAThuAAEAAAHTJAOj MACLEAN CHAINED_ROWS 29897 AAAThuAAEAAAHTJAOk MACLEAN COMPRESS_QUERY1 29897 8 rows selected. select dbms_rowid.rowid_block_number(rowid),dbms_rowid.rowid_relative_fno(rowid) from hcc_maclean where owner='MACLEAN'; session A: update hcc_maclean set OBJECT_NAME=OBJECT_NAME||'DBM' where rowid='AAAThuAAEAAAHTJAOI'; session B: update hcc_maclean set OBJECT_NAME=OBJECT_NAME||'DBM' where rowid='AAAThuAAEAAAHTJAOJ'; SQL> select sid,wait_event_text,BLOCKER_SID from v$wait_chains; SID WAIT_EVENT_TEXT BLOCKER_SID ---------- ---------------------------------------------------------------- ----------- 13 enq: TX - row lock contention 136 136 SQL*Net message from client ????session A block B,????HCC???update row??CU?????CU?????? SQL> alter system checkpoint; System altered. SQL> / System altered. SQL> alter system dump datafile 4 block 29897 2 ; Block header dump: 0x010074c9 Object id on Block? Y seg/obj: 0x1386e csc: 0x00.1cad7e itc: 3 flg: E typ: 1 - DATA brn: 0 bdba: 0x10074c8 ver: 0x01 opc: 0 inc: 0 exflg: 0 Itl Xid Uba Flag Lck Scn/Fsc 0x01 0xffff.000.00000000 0x00000000.0000.00 C--- 0 scn 0x0000.001cabfa 0x02 0x000a.00a.00000430 0x00c051a7.0169.17 ---- 1 fsc 0x0000.00000000 0x03 0x0000.000.00000000 0x00000000.0000.00 ---- 0 fsc 0x0000.00000000 avsp=0x14 tosp=0x14 r0_9ir2=0x0 mec_kdbh9ir2=0x0 76543210 shcf_kdbh9ir2=---------- 76543210 flag_9ir2=--R----- Archive compression: Y fcls_9ir2[0]={ } 0x16:pti[0] nrow=1 offs=0 0x1a:pri[0] offs=0x30 block_row_dump: tab 0, row 0, @0x30 tl: 8016 fb: --H-F--N lb: 0x2 cc: 1 ==>??CU??ITL 0x02 nrid: 0x010074ca.0 col 0: [8004] Compression level: 02 (Query High) Length of CU row: 8004 kdzhrh: ------PC CBLK: 1 Start Slot: 00 NUMP: 01 PNUM: 00 POFF: 7984 PRID: 0x010074ca.0 CU header: CU version: 0 CU magic number: 0x4b445a30 CU checksum: 0xf8faf86e CU total length: 8694 CU flags: NC-U-CRD-OP ncols: 15 nrows: 995 algo: 0 CU decomp length: 8487 len/value length: 100111 row pieces per row: 1 num deleted rows: 1 deleted rows: 904, START_CU: ????????????row?????: SQL> select DBMS_COMPRESSION.GET_COMPRESSION_TYPE('SCOTT','HCC_MACLEAN','AAAThuAAEAAAHTJAOk') from dual; DBMS_COMPRESSION.GET_COMPRESSION_TYPE('SCOTT','HCC_MACLEAN','AAATHUAAEAAAHTJAOK' -------------------------------------------------------------------------------- 4 COMP_NOCOMPRESS CONSTANT NUMBER := 1;COMP_FOR_OLTP CONSTANT NUMBER := 2;COMP_FOR_QUERY_HIGH CONSTANT NUMBER := 4;COMP_FOR_QUERY_LOW CONSTANT NUMBER := 8;COMP_FOR_ARCHIVE_HIGH CONSTANT NUMBER := 16;COMP_FOR_ARCHIVE_LOW CONSTANT NUMBER := 32; COMP_RATIO_MINROWS CONSTANT NUMBER := 1000000;COMP_RATIO_ALLROWS CONSTANT NUMBER := -1; ?????????????,??COMP_FOR_QUERY_HIGH?4,COMP_FOR_QUERY_LOW ?8 ?????????GET_COMPRESSION_TYPE??rowid????????4?????COMP_FOR_QUERY_HIGH????: SQL> update hcc_maclean set OBJECT_NAME=OBJECT_NAME||'DBM' where owner='MACLEAN'; 8 rows updated. SQL> commit; Commit complete. SQL> select DBMS_COMPRESSION.GET_COMPRESSION_TYPE('SCOTT','HCC_MACLEAN',rowid) from HCC_MACLEAN where owner='MACLEAN'; DBMS_COMPRESSION.GET_COMPRESSION_TYPE('SCOTT','HCC_MACLEAN',ROWID) ------------------------------------------------------------------ 1 1 1 1 1 1 1 1 8 rows selected. ??????????????COMPRESSION_TYPE?COMP_FOR_QUERY_HIGH???COMP_NOCOMPRESS,????????compress for query high????????????????? ?11g????????????????????HCC??????????? ALTER TABLE MOVE???????????????????HCC??? SQL> ALTER TABLE hcc_MACLEAN move COMPRESS FOR ARCHIVE HIGH; Table altered. SQL> select DBMS_COMPRESSION.GET_COMPRESSION_TYPE('SCOTT','HCC_MACLEAN',rowid) from HCC_MACLEAN where owner='MACLEAN'; DBMS_COMPRESSION.GET_COMPRESSION_TYPE('SCOTT','HCC_MACLEAN',ROWID) ------------------------------------------------------------------ 16 16 16 16 16 16 16 16 8 rows selected.

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• Server to server replication and CPU and 32k\ corrupt doc

  - by nick wall

  Summary: if database contains a doc with 32K issue or corrupt, on server to server replication it causes marked increase in CPU in nserver.exe task, which effectively causes our server(s) to slow right down. We have a 5 server cluster (1 "hub" and 4 HTTP servers accessed via reverse proxy and SSO for load balancing and redundancy). All are physically located next to each other on network, they don't have dedicated network\ ports for cluster or replication. I realise IBM recommendation is dedicated port for cluster. Cluster queues are in tolerance and under heavy application user load, i.e. the maximum number of documents are being created, edited, deleted, the replication times between servers are negligible. Normally, all is well. Of the servers in the cluster, 1 is considered the "hub", and imitates a PUSH-PULL replication with it's cluster mates every 60mins, so that the replication load is taken by the hub and not cluster mates. The problem we have: every now and then we get a slow replication time from the hub to a cluster mate, sometimes up to 30mins. This maxes out the nserver.exe task on the "cluster mate" which causes it to respond to http requests very slowly. In the past, we have found that if a corrupt document is in the DB, it can have this affect, but on those occasions, the server log will show the corrupt doc noteId, we run fixup, all well. But we are not now seeing any record of corrupt docs. What we have noticed is if a doc with the 32K issue is present, the same thing can happen. Our only solution in that case is to run a : fixup mydb.nsf -V, which shows it is purging a 32K doc. Luckily we run a reverse proxy, so we can shut HTTP servers down without users noticing, but users do notice when a server has the problem! Has anyone else seen this occur? I have set up DDM event handlers for many of the replication events. I have set the replication time out limit to 5 mins (the max we usually see under full user load is 0.1min), to prevent it rep'ing for 30mins as before. This ia a temporary work around. Does anyone know of a DDM event to trap the 32K issue? we could at least then send alert. Regarding 32K issue: this prob needs another thread, but we are finding this relatively hard to find the source of the issue as the 32K event is fairly rare. Our app is fairly complex, interacting with various other external web services, with 2 way data transfer. But if we do encounter a 32K doc, we can't look at field properties, so we can't work out which field has issue which would give us a clue as to which process is culprit. As above, we run a fixup -V. Any help\ comments on this would be gratefully received.

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• What DNS server to use for dynamic load-balancing of website?

  - by Marki555

  I will have 2 servers in different datacenters (different countries) and I want to use DNS load-balancing mainly for High Availability of website hosted on those 2 servers. It is just ad tracking site, which records hit in local database and returns few lines on html code. I want to return 2 A records each time because of DNS pinning in browsers (if one server fails, browser will try second A record which it has already cached). Both servers will be acting also as DNS servers for redundancy. Now comes my proposed solution: I will use BIND and have both servers as a master for that zone. On each server there will be running script, which will periodically test availability (http) of both servers and remove IP from DNS in case of failure. Now the questions :) 1) Is BIND suitable for this solution? I think BIND performance is good and it is easy to manipulate the zone file via script. And as I will modify the zone only in case of failure/maintenance, the modifications (and thus bind reload) won't be often. 2) I plan to use TTL of 5 minutes. The website will have about 1000-3000 req/s but from distinct clients (each IP only 1-3 requests), so I think the DNS load won't be too much. I suppose their ISPs will cache the responses for those 5 mins. Is there any reason to lower the TTL even more? 3) Is my master-master approach good? Or should I make one of the servers master and the other one slave? Right now each server can monitor both itself and the other one. If only webservice fails, both DNS nodes will notice it. If the whole server fails, then the remaining DNS node will notice it and the failed node will not answer DNS queries anyway. 4) Is it a big issue when one NS server does not respond to queries? If yes, I can make a third DNS, so anytime at least 2 of them would accept queries... 5) Should I rewrite the zone file via script, or just use dynamic DNS update (for example via nsupdateutility)?

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