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• What would be equivalent of Number(4) of Oracle database to MySQL Datatype ?

  - by Rachel

  What would be equivalent of Number(4) of Oracle database to MySQL Datatype ?

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• A way to search form table in MySQL database.

  - by Eugene

  I looked for a way to scan database for a specific table. For example i have: Database: system_ultimate Table: system_settings And let us say, that one doesn't know precise name of the table. He only knows, that it is some how connected to word settings. How could he search for that table name then? I understand, that usually people who develop know, what they develop, but I'm trying to get hang of MVC and I'm trying to stay as far away as possible from direct communication with table using the name. I know, that to see all tables I could use SHOW TABLES;

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• How can I write my code to attempt a database action but continue executing code on failure?

  - by Chris

  Simple question I guess, I want to use PHP to write an update to an existing row in my database, if it doesn't happen I want to log the failure but continue executing the code. While it would be nice to have records of failures to track down issues, that the update failed isn't that important to my user, nor will it affect the running of any other code; the query is simply for a 'cosmetic' but entirely unnecessary piece of information. My database class's query function is set to die on failure, could I modify that or is there another way of doing it without altering my standard query code?

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• Tuples vs. Anonymous Types vs. Expando object. (in regards to LINQ queries)

  - by punkouter

  I am a beginner who finally started understanding anonymous types. (see old post http://stackoverflow.com/questions/3010147/what-is-the-return-type-for-a-anonymous-linq-query-select-what-is-the-best-way-t) So in LINQ queries you form the type of return value you want within the linq query right? It seems the way to do this is anonymous type right? Can someone explain to me if and when I could use a Tuple/Expando object instead? They all seem very simliar?

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• Migrating SQL Server Databases – The DBA’s Checklist (Part 3)

  - by Sadequl Hussain

  Continuing from Part 2 of the Database Migration Checklist series: Step 10: Full-text catalogs and full-text indexing This is one area of SQL Server where people do not seem to take notice unless something goes wrong. Full-text functionality is a specialised area in database application development and is not usually implemented in your everyday OLTP systems. Nevertheless, if you are migrating a database that uses full-text indexing on one or more tables, you need to be aware a few points. First of all, SQL Server 2005 now allows full-text catalog files to be restored or attached along with the rest of the database. However, after migration, if you are unable to look at the properties of any full-text catalogs, you are probably better off dropping and recreating it. You may also get the following error messages along the way: Msg 9954, Level 16, State 2, Line 1 The Full-Text Service (msftesql) is disabled. The system administrator must enable this service. This basically means full text service is not running (disabled or stopped) in the destination instance. You will need to start it from the Configuration Manager. Similarly, if you get the following message, you will also need to drop and recreate the catalog and populate it. Msg 7624, Level 16, State 1, Line 1 Full-text catalog ‘catalog_name‘ is in an unusable state. Drop and re-create this full-text catalog. A full population of full-text indexes can be a time and resource intensive operation. Obviously you will want to schedule it for low usage hours if the database is restored in an existing production server. Also, bear in mind that any scheduled job that existed in the source server for populating the full text catalog (e.g. nightly process for incremental update) will need to be re-created in the destination. Step 11: Database collation considerations Another sticky area to consider during a migration is the collation setting. Ideally you would want to restore or attach the database in a SQL Server instance with the same collation. Although not used commonly, SQL Server allows you to change a database’s collation by using the ALTER DATABASE command: ALTER DATABASE database_name COLLATE collation_name You should not be using this command for no reason as it can get really dangerous.  When you change the database collation, it does not change the collation of the existing user table columns.  However the columns of every new table, every new UDT and subsequently created variables or parameters in code will use the new setting. The collation of every char, nchar, varchar, nvarchar, text or ntext field of the system tables will also be changed. Stored procedure and function parameters will be changed to the new collation and finally, every character-based system data type and user defined data types will also be affected. And the change may not be successful either if there are dependent objects involved. You may get one or multiple messages like the following: Cannot ALTER ‘object_name‘ because it is being referenced by object ‘dependent_object_name‘. That is why it is important to test and check for collation related issues. Collation also affects queries that use comparisons of character-based data.  If errors arise due to two sides of a comparison being in different collation orders, the COLLATE keyword can be used to cast one side to the same collation as the other. Continues…

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• SQL Server source control from Visual Studio

  - by David Atkinson

  Developers have long since had to context switch between two IDEs, Visual Studio for application code development and SQL Server Management Studio for database development. While this is accepted, especially given the richness of the database development feature set in SSMS, loading a separate tool can seem a little overkill. This is where SQL Connect comes in. This is an add-in to Visual Studio that provides a connected development experience for the SQL Server developer. Connected database development involves modifying a development sandbox database, as opposed to offline development, where SQL text files are modified independently of the database. One of the main complaints of Data Dude (VS DBPro) is that it enforces the offline approach. This gripe is what SQL Connect addresses. If you don't already use SQL Source Control, you can get up and running with SQL Connect by adding a new project to your Visual Studio solution as follows: Then choose your existing development database and you're ready to go. If you already use SQL Source Control, you will need to link SQL Connect to your existing database scripts folder repository, so SQL Connect and SQL Source Control can be used collaboratively (note that SQL Source Control v.3.0.9.18 or later is required). Locate the repository (this can be found in the Setup tab in SQL Source Control). .and create a working folder for it (here I'm using TortoiseSVN). Back in Visual Studio, locate the SQL Connect panel (in the View menu if it hasn't auto loaded) and select Import SQL Source Control project Locate your working folder and click Import. This creates a Red Gate database project under your solution: From here you can modify your development database, and manage your changes in source control. To associate your development database with the project, right click on the project node, select Properties, set the database and Save. Now you're ready to make some changes. Locate the object you'd like to modify in the Solution Explorer, and double click it to invoke a query window or table designer. You also have the option to edit the creation SQL directly using Edit SQL File in Project. Keeping the development database and Visual Studio project in sync is as easy as clicking on a button. One you've made your change, you can use whichever mechanism you choose to commit to source control. Here I'm using the free open-source AnkhSVN to integrate Subversion with Visual Studio. Maintaining your database in a Visual Studio solution means that you can commit database changes and application code changes in the same changeset. This is desirable if you have continuous integration set up as you want to ensure that all files related to a change are committed atomically, so you avoid an interim "broken build". More discussion on SQL Connect and its benefits can be found in the following article on Simple Talk: No More Disconnected SQL Development in Visual Studio The SQL Connect project team is currently assessing the backlog for the next development effort, and they'd appreciate your feature suggestions, as well as your votes on their suggestions site: http://redgate.uservoice.com/forums/140800-sql-connect-for-visual-studio- A 28-day free trial of SQL Connect is available from the Red Gate website. Technorati Tags: SQL Server

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• Protecting Consolidated Data on Engineered Systems

  - by Steve Enevold

  In this time of reduced budgets and cost cutting measures in Federal, State and Local governments, the requirement to provide services continues to grow. Many agencies are looking at consolidating their infrastructure to reduce cost and meet budget goals. Oracle's engineered systems are ideal platforms for accomplishing these goals. These systems provide unparalleled performance that is ideal for running applications and databases that traditionally run on separate dedicated environments. However, putting multiple critical applications and databases in a single architecture makes security more critical. You are putting a concentrated set of sensitive data on a single system, making it a more tempting target.  The environments were previously separated by iron so now you need to provide assurance that one group, department, or application's information is not visible to other personnel or applications resident in the Exadata system. Administration of the environments requires formal separation of duties so an administrator of one application environment cannot view or negatively impact others. Also, these systems need to be in protected environments just like other critical production servers. They should be in a data center protected by physical controls, network firewalls, intrusion detection and prevention, etc Exadata also provides unique security benefits, including a reducing attack surface by minimizing packages and services to only those required. In addition to reducing the possible system areas someone may attempt to infiltrate, Exadata has the following features: 1.    Infiniband, which functions as a secure private backplane 2.    IPTables  to perform stateful packet inspection for all nodes               Cellwall implements firewall services on each cell using IPTables 3.    Hardware accelerated encryption for data at rest on storage cells Oracle is uniquely positioned to provide the security necessary for implementing Exadata because security has been a core focus since the company's beginning. In addition to the security capabilities inherent in Exadata, Oracle security products are all certified to run in an Exadata environment. Database Vault Oracle Database Vault helps organizations increase the security of existing applications and address regulatory mandates that call for separation-of-duties, least privilege and other preventive controls to ensure data integrity and data privacy. Oracle Database Vault proactively protects application data stored in the Oracle database from being accessed by privileged database users. A unique feature of Database Vault is the ability to segregate administrative tasks including when a command can be executed, or that the DBA can manage the health of the database and objects, but may not see the data Advanced Security  helps organizations comply with privacy and regulatory mandates by transparently encrypting all application data or specific sensitive columns, such as credit cards, social security numbers, or personally identifiable information (PII). By encrypting data at rest and whenever it leaves the database over the network or via backups, Oracle Advanced Security provides the most cost-effective solution for comprehensive data protection. Label Security  is a powerful and easy-to-use tool for classifying data and mediating access to data based on its classification. Designed to meet public-sector requirements for multi-level security and mandatory access control, Oracle Label Security provides a flexible framework that both government and commercial entities worldwide can use to manage access to data on a "need to know" basis in order to protect data privacy and achieve regulatory compliance  Data Masking reduces the threat of someone in the development org taking data that has been copied from production to the development environment for testing, upgrades, etc by irreversibly replacing the original sensitive data with fictitious data so that production data can be shared safely with IT developers or offshore business partners  Audit Vault and Database Firewall Oracle Audit Vault and Database Firewall serves as a critical detective and preventive control across multiple operating systems and database platforms to protect against the abuse of legitimate access to databases responsible for almost all data breaches and cyber attacks.  Consolidation, cost-savings, and performance can now be achieved without sacrificing security. The combination of built in protection and Oracle’s industry-leading data protection solutions make Exadata an ideal platform for Federal, State, and local governments and agencies.

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• How to populate RRD database with CPU and MEM usage data?

  - by Tomaszs

  I have a Lighttpd server (on Centos) and would like to display 4 graphs: lighttpd traffic, lighttpd requests per second, CPU usage and MEM usage. I've set place for rrd database for lighttpd config like this: rrdtool.binary = "/usr/bin/rrdtool" rrdtool.db-name = "/var/www/lighttpd.rrd" And put into my WWW cgi-bin sh file that gets data from lighttpd RRD file and creates graphs of traffic and requests per second like this: #!/bin/sh RRDTOOL=/usr/bin/rrdtool OUTDIR=//var/www/graphs INFILE=/var/www/lighttpd.rrd OUTPRE=lighttpd-traffic WIDTH=400 HEIGHT=100 DISP="-v bytes --title TrafficWebserver \ DEF:binraw=$INFILE:InOctets:AVERAGE \ DEF:binmaxraw=$INFILE:InOctets:MAX \ DEF:binminraw=$INFILE:InOctets:MIN \ DEF:bout=$INFILE:OutOctets:AVERAGE \ DEF:boutmax=$INFILE:OutOctets:MAX \ DEF:boutmin=$INFILE:OutOctets:MIN \ CDEF:bin=binraw,-1,* \ CDEF:binmax=binmaxraw,-1,* \ CDEF:binmin=binminraw,-1,* \ CDEF:binminmax=binmaxraw,binminraw,- \ CDEF:boutminmax=boutmax,boutmin,- \ AREA:binmin#ffffff: \ STACK:binmax#f00000: \ LINE1:binmin#a0a0a0: \ LINE1:binmax#a0a0a0: \ LINE2:bin#efb71d:incoming \ GPRINT:bin:MIN:%.2lf \ GPRINT:bin:AVERAGE:%.2lf \ GPRINT:bin:MAX:%.2lf \ AREA:boutmin#ffffff: \ STACK:boutminmax#00f000: \ LINE1:boutmin#a0a0a0: \ LINE1:boutmax#a0a0a0: \ LINE2:bout#a0a735:outgoing \ GPRINT:bout:MIN:%.2lf \ GPRINT:bout:AVERAGE:%.2lf \ GPRINT:bout:MAX:%.2lf \ " $RRDTOOL graph $OUTDIR/$OUTPRE-hour.png -a PNG --start -14400 $DISP -w $WIDTH -h $HEIGHT $RRDTOOL graph $OUTDIR/$OUTPRE-day.png -a PNG --start -86400 $DISP -w $WIDTH -h $HEIGHT $RRDTOOL graph $OUTDIR/$OUTPRE-month.png -a PNG --start -2592000 $DISP -w $WIDTH -h $HEIGHT OUTPRE=lighttpd-requests DISP="-v req --title RequestsperSecond -u 1 \ DEF:req=$INFILE:Requests:AVERAGE \ DEF:reqmax=$INFILE:Requests:MAX \ DEF:reqmin=$INFILE:Requests:MIN \ CDEF:reqminmax=reqmax,reqmin,- \ AREA:reqmin#ffffff: \ STACK:reqminmax#00f000: \ LINE1:reqmin#a0a0a0: \ LINE1:reqmax#a0a0a0: \ LINE2:req#00a735:requests" $RRDTOOL graph $OUTDIR/$OUTPRE-hour.png -a PNG --start -14400 $DISP -w $WIDTH -h $HEIGHT $RRDTOOL graph $OUTDIR/$OUTPRE-day.png -a PNG --start -86400 $DISP -w $WIDTH -h $HEIGHT $RRDTOOL graph $OUTDIR/$OUTPRE-month.png -a PNG --start -2592000 $DISP -w $WIDTH -h $HEIGHT Basically it's not my script, i get it from somewhere from the internet. Now i would like to do the same for CPU usage and MEM usage. I don't like to use any additional packages! As you can see lighttpd populates lighttpd.rrd file with traffic data and requests per second. Now i would like to the system to populate second rrd file with CPU and MEM usage, so i can add to sh file code to generate graphs for this data. How can I populate RRD file with CPU and MEM usage data? Please, NO THIRD-PARTY tools !

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• General monitoring for SQL Server Analysis Services using Performance Monitor

  - by Testas

  A recent customer engagement required a setup of a monitoring solution for SSAS, due to the time restrictions placed upon this, native Windows Performance Monitor (Perfmon) and SQL Server Profiler Monitoring Tools was used as using a third party tool would have meant the customer providing an additional monitoring server that was not available.I wanted to outline the performance monitoring counters that was used to monitor the system on which SSAS was running. Due to the slow query performance that was occurring during certain scenarios, perfmon was used to establish if any pressure was being placed on the Disk, CPU or Memory subsystem when concurrent connections access the same query, and Profiler to pinpoint how the query was being managed within SSAS, profiler I will leave for another blogThis guide is not designed to provide a definitive list of what should be used when monitoring SSAS, different situations may require the addition or removal of counters as presented by the situation. However I hope that it serves as a good basis for starting your monitoring of SSAS. I would also like to acknowledge Chris Webb’s awesome chapters from “Expert Cube Development” that also helped shape my monitoring strategy:http://cwebbbi.spaces.live.com/blog/cns!7B84B0F2C239489A!6657.entrySimulating ConnectionsTo simulate the additional connections to the SSAS server whilst monitoring, I used ascmd to simulate multiple connections to the typical and worse performing queries that were identified by the customer. A similar sript can be downloaded from codeplex at http://www.codeplex.com/SQLSrvAnalysisSrvcs.     File name: ASCMD_StressTestingScripts.zip. Performance MonitorWithin performance monitor,  a counter log was created that contained the list of counters below. The important point to note when running the counter log is that the RUN AS property within the counter log properties should be changed to an account that has rights to the SSAS instance when monitoring MSAS counters. Failure to do so means that the counter log runs under the system account, no errors or warning are given while running the counter log, and it is not until you need to view the MSAS counters that they will not be displayed if run under the default account that has no right to SSAS. If your connection simulation takes hours, this could prove quite frustrating if not done beforehand JThe counters used……  Object Counter Instance Justification System Processor Queue legnth N/A Indicates how many threads are waiting for execution against the processor. If this counter is consistently higher than around 5 when processor utilization approaches 100%, then this is a good indication that there is more work (active threads) available (ready for execution) than the machine's processors are able to handle. System Context Switches/sec N/A Measures how frequently the processor has to switch from user- to kernel-mode to handle a request from a thread running in user mode. The heavier the workload running on your machine, the higher this counter will generally be, but over long term the value of this counter should remain fairly constant. If this counter suddenly starts increasing however, it may be an indicating of a malfunctioning device, especially if the Processor\Interrupts/sec\(_Total) counter on your machine shows a similar unexplained increase Process % Processor Time sqlservr Definately should be used if Processor\% Processor Time\(_Total) is maxing at 100% to assess the effect of the SQL Server process on the processor Process % Processor Time msmdsrv Definately should be used if Processor\% Processor Time\(_Total) is maxing at 100% to assess the effect of the SQL Server process on the processor Process Working Set sqlservr If the Memory\Available bytes counter is decreaing this counter can be run to indicate if the process is consuming larger and larger amounts of RAM. Process(instance)\Working Set measures the size of the working set for each process, which indicates the number of allocated pages the process can address without generating a page fault. Process Working Set msmdsrv If the Memory\Available bytes counter is decreaing this counter can be run to indicate if the process is consuming larger and larger amounts of RAM. Process(instance)\Working Set measures the size of the working set for each process, which indicates the number of allocated pages the process can address without generating a page fault. Processor % Processor Time _Total and individual cores measures the total utilization of your processor by all running processes. If multi-proc then be mindful only an average is provided Processor % Privileged Time _Total To see how the OS is handling basic IO requests. If kernel mode utilization is high, your machine is likely underpowered as it's too busy handling basic OS housekeeping functions to be able to effectively run other applications. Processor % User Time _Total To see how the applications is interacting from a processor perspective, a high percentage utilisation determine that the server is dealing with too many apps and may require increasing thje hardware or scaling out Processor Interrupts/sec _Total  The average rate, in incidents per second, at which the processor received and serviced hardware interrupts. Shoulr be consistant over time but a sudden unexplained increase could indicate a device malfunction which can be confirmed using the System\Context Switches/sec counter Memory Pages/sec N/A Indicates the rate at which pages are read from or written to disk to resolve hard page faults. This counter is a primary indicator of the kinds of faults that cause system-wide delays, this is the primary counter to watch for indication of possible insufficient RAM to meet your server's needs. A good idea here is to configure a perfmon alert that triggers when the number of pages per second exceeds 50 per paging disk on your system. May also want to see the configuration of the page file on the Server Memory Available Mbytes N/A is the amount of physical memory, in bytes, available to processes running on the computer. if this counter is greater than 10% of the actual RAM in your machine then you probably have more than enough RAM. monitor it regularly to see if any downward trend develops, and set an alert to trigger if it drops below 2% of the installed RAM. Physical Disk Disk Transfers/sec for each physical disk If it goes above 10 disk I/Os per second then you've got poor response time for your disk. Physical Disk Idle Time _total If Disk Transfers/sec is above  25 disk I/Os per second use this counter. which measures the percent time that your hard disk is idle during the measurement interval, and if you see this counter fall below 20% then you've likely got read/write requests queuing up for your disk which is unable to service these requests in a timely fashion. Physical Disk Disk queue legnth For the OLAP and SQL physical disk A value that is consistently less than 2 means that the disk system is handling the IO requests against the physical disk Network Interface Bytes Total/sec For the NIC Should be monitored over a period of time to see if there is anb increase/decrease in network utilisation Network Interface Current Bandwidth For the NIC is an estimate of the current bandwidth of the network interface in bits per second (BPS). MSAS 2005: Memory Memory Limit High KB N/A Shows (as a percentage) the high memory limit configured for SSAS in C:\Program Files\Microsoft SQL Server\MSAS10.MSSQLSERVER\OLAP\Config\msmdsrv.ini MSAS 2005: Memory Memory Limit Low KB N/A Shows (as a percentage) the low memory limit configured for SSAS in C:\Program Files\Microsoft SQL Server\MSAS10.MSSQLSERVER\OLAP\Config\msmdsrv.ini MSAS 2005: Memory Memory Usage KB N/A Displays the memory usage of the server process. MSAS 2005: Memory File Store KB N/A Displays the amount of memory that is reserved for the Cache. Note if total memory limit in the msmdsrv.ini is set to 0, no memory is reserved for the cache MSAS 2005: Storage Engine Query Queries from Cache Direct / sec N/A Displays the rate of queries answered from the cache directly MSAS 2005: Storage Engine Query Queries from Cache Filtered / Sec N/A Displays the Rate of queries answered by filtering existing cache entry. MSAS 2005: Storage Engine Query Queries from File / Sec N/A Displays the Rate of queries answered from files. MSAS 2005: Storage Engine Query Average time /query N/A Displays the average time of a query MSAS 2005: Connection Current connections N/A Displays the number of connections against the SSAS instance MSAS 2005: Connection Requests / sec N/A Displays the rate of query requests per second MSAS 2005: Locks Current Lock Waits N/A Displays thhe number of connections waiting on a lock MSAS 2005: Threads Query Pool job queue Length N/A The number of queries in the job queue MSAS 2005:Proc Aggregations Temp file bytes written/sec N/A Shows the number of bytes of data processed in a temporary file MSAS 2005:Proc Aggregations Temp file rows written/sec N/A Shows the number of bytes of data processed in a temporary file 

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• SQL SERVER – Faster SQL Server Databases and Applications – Power and Control with SafePeak Caching Options

  - by Pinal Dave

  Update: This blog post is written based on the SafePeak, which is available for free download. Today, I’d like to examine more closely one of my preferred technologies for accelerating SQL Server databases, SafePeak. Safepeak’s software provides a variety of advanced data caching options, techniques and tools to accelerate the performance and scalability of SQL Server databases and applications. I’d like to look more closely at some of these options, as some of these capabilities could help you address lagging database and performance on your systems. To better understand the available options, it is best to start by understanding the difference between the usual “Basic Caching” vs. SafePeak’s “Dynamic Caching”. Basic Caching Basic Caching (or the stale and static cache) is an ability to put the results from a query into cache for a certain period of time. It is based on TTL, or Time-to-live, and is designed to stay in cache no matter what happens to the data. For example, although the actual data can be modified due to DML commands (update/insert/delete), the cache will still hold the same obsolete query data. Meaning that with the Basic Caching is really static / stale cache.  As you can tell, this approach has its limitations. Dynamic Caching Dynamic Caching (or the non-stale cache) is an ability to put the results from a query into cache while maintaining the cache transaction awareness looking for possible data modifications. The modifications can come as a result of: DML commands (update/insert/delete), indirect modifications due to triggers on other tables, executions of stored procedures with internal DML commands complex cases of stored procedures with multiple levels of internal stored procedures logic. When data modification commands arrive, the caching system identifies the related cache items and evicts them from cache immediately. In the dynamic caching option the TTL setting still exists, although its importance is reduced, since the main factor for cache invalidation (or cache eviction) become the actual data updates commands. Now that we have a basic understanding of the differences between “basic” and “dynamic” caching, let’s dive in deeper. SafePeak: A comprehensive and versatile caching platform SafePeak comes with a wide range of caching options. Some of SafePeak’s caching options are automated, while others require manual configuration. Together they provide a complete solution for IT and Data managers to reach excellent performance acceleration and application scalability for  a wide range of business cases and applications. Automated caching of SQL Queries: Fully/semi-automated caching of all “read” SQL queries, containing any types of data, including Blobs, XMLs, Texts as well as all other standard data types. SafePeak automatically analyzes the incoming queries, categorizes them into SQL Patterns, identifying directly and indirectly accessed tables, views, functions and stored procedures; Automated caching of Stored Procedures: Fully or semi-automated caching of all read” stored procedures, including procedures with complex sub-procedure logic as well as procedures with complex dynamic SQL code. All procedures are analyzed in advance by SafePeak’s  Metadata-Learning process, their SQL schemas are parsed – resulting with a full understanding of the underlying code, objects dependencies (tables, views, functions, sub-procedures) enabling automated or semi-automated (manually review and activate by a mouse-click) cache activation, with full understanding of the transaction logic for cache real-time invalidation; Transaction aware cache: Automated cache awareness for SQL transactions (SQL and in-procs); Dynamic SQL Caching: Procedures with dynamic SQL are pre-parsed, enabling easy cache configuration, eliminating SQL Server load for parsing time and delivering high response time value even in most complicated use-cases; Fully Automated Caching: SQL Patterns (including SQL queries and stored procedures) that are categorized by SafePeak as “read and deterministic” are automatically activated for caching; Semi-Automated Caching: SQL Patterns categorized as “Read and Non deterministic” are patterns of SQL queries and stored procedures that contain reference to non-deterministic functions, like getdate(). Such SQL Patterns are reviewed by the SafePeak administrator and in usually most of them are activated manually for caching (point and click activation); Fully Dynamic Caching: Automated detection of all dependent tables in each SQL Pattern, with automated real-time eviction of the relevant cache items in the event of “write” commands (a DML or a stored procedure) to one of relevant tables. A default setting; Semi Dynamic Caching: A manual cache configuration option enabling reducing the sensitivity of specific SQL Patterns to “write” commands to certain tables/views. An optimization technique relevant for cases when the query data is either known to be static (like archive order details), or when the application sensitivity to fresh data is not critical and can be stale for short period of time (gaining better performance and reduced load); Scheduled Cache Eviction: A manual cache configuration option enabling scheduling SQL Pattern cache eviction based on certain time(s) during a day. A very useful optimization technique when (for example) certain SQL Patterns can be cached but are time sensitive. Example: “select customers that today is their birthday”, an SQL with getdate() function, which can and should be cached, but the data stays relevant only until 00:00 (midnight); Parsing Exceptions Management: Stored procedures that were not fully parsed by SafePeak (due to too complex dynamic SQL or unfamiliar syntax), are signed as “Dynamic Objects” with highest transaction safety settings (such as: Full global cache eviction, DDL Check = lock cache and check for schema changes, and more). The SafePeak solution points the user to the Dynamic Objects that are important for cache effectiveness, provides easy configuration interface, allowing you to improve cache hits and reduce cache global evictions. Usually this is the first configuration in a deployment; Overriding Settings of Stored Procedures: Override the settings of stored procedures (or other object types) for cache optimization. For example, in case a stored procedure SP1 has an “insert” into table T1, it will not be allowed to be cached. However, it is possible that T1 is just a “logging or instrumentation” table left by developers. By overriding the settings a user can allow caching of the problematic stored procedure; Advanced Cache Warm-Up: Creating an XML-based list of queries and stored procedure (with lists of parameters) for periodically automated pre-fetching and caching. An advanced tool allowing you to handle more rare but very performance sensitive queries pre-fetch them into cache allowing high performance for users’ data access; Configuration Driven by Deep SQL Analytics: All SQL queries are continuously logged and analyzed, providing users with deep SQL Analytics and Performance Monitoring. Reduce troubleshooting from days to minutes with database objects and SQL Patterns heat-map. The performance driven configuration helps you to focus on the most important settings that bring you the highest performance gains. Use of SafePeak SQL Analytics allows continuous performance monitoring and analysis, easy identification of bottlenecks of both real-time and historical data; Cloud Ready: Available for instant deployment on Amazon Web Services (AWS). As you can see, there are many options to configure SafePeak’s SQL Server database and application acceleration caching technology to best fit a lot of situations. If you’re not familiar with their technology, they offer free-trial software you can download that comes with a free “help session” to help get you started. You can access the free trial here. Also, SafePeak is available to use on Amazon Cloud. Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• SQL SERVER – Weekly Series – Memory Lane – #031

  - by Pinal Dave

  Here is the list of selected articles of SQLAuthority.com across all these years. Instead of just listing all the articles I have selected a few of my most favorite articles and have listed them here with additional notes below it. Let me know which one of the following is your favorite article from memory lane. 2007 Find Table without Clustered Index – Find Table with no Primary Key Clustered index is very important concept for any table. They impact the performance very heavily. Here is a quick script to find tables without a clustered index. Replace TEXT with VARCHAR(MAX) – Stop using TEXT, NTEXT, IMAGE Data Types Question: “Is VARCHAR (MAX) big enough to store the TEXT field?” Answer: “Yes, VARCHAR(MAX) is big enough to accommodate TEXT field. TEXT, NTEXT and IMAGE data types of SQL Server 2000 will be deprecated in a future version of SQL Server, SQL Server 2005 provides backward compatibility to data types but it is recommended to use new data types which are VARHCAR (MAX), NVARCHAR (MAX) and VARBINARY (MAX).” Limiting Result Sets by Using TABLESAMPLE – Examples Introduced in SQL Server 2005, TABLESAMPLE allows you to extract a sampling of rows from a table in the FROM clause. The rows retrieved are random and they are are not in any order. This sampling can be based on a percentage of number of rows. You can use TABLESAMPLE when only a sampling of rows is necessary for the application instead of a full result set. User Defined Functions (UDF) Limitations UDF have its own advantage and usage but in this article we will see the limitation of UDF. Things UDF can not do and why Stored Procedure are considered as more flexible then UDFs. Stored Procedure are more flexibility then User Defined Functions(UDF). However, this blog post is a good read to know what are the limitations of UDF. Change Database Compatible Level – Backward Compatibility For a long time SQL Server stayed on the compatibility level of 80 which is of SQL Server 2000. However, as soon as SQL Server 2005 introduced the issue of compatibility was quite a major issue. Since that time MS has been releasing the versions at every 2-3 years, changing compatibility is a ever popular topic. In this blog post, we learn how we can do the same using T-SQL. We can also do the same using SSMS and here is the blog post for the same: Change Database Compatible Level – Backward Compatibility – Part 2 – Management Studio. Constraint on VARCHAR(MAX) Field To Limit It Certain Length How can I limit the VARCHAR(MAX) field with maximum length of 12500 characters only. His Question was valid as our application was allowed 12500 characters. First of all – this requirement is bit strange but if someone wants to do the same, they can do it as described in this blog post. 2008 UNPIVOT Table Example Understanding UNPIVOT can be very complicated at times. In this blog post, I have attempted to explain the same concept in very simple words. Create Default Constraint Over Table Column A simple straight to script blog post – I still use this blog quite many times for my own reference. UDF – Get the Day of the Week Function It took me 4 iteration to find this very simple function which can immediately get the day of the week in a single line. 2009 Find Hostname and Current Logged In User Name There are two tricks listed in this blog post where users can find out the hostname and current logged user name immediately and very easily. Interesting Observation of Logon Trigger On All Servers When I was doing a project, I made an interesting observation of executing a logon trigger multiple times. It was absolutely unexpected for me! As I was logging only once, naturally, I was expecting the entry only once. However, it did it multiple times on different threads – indeed an eccentric phenomenon at first sight! Difference Between Candidate Keys and Primary Key One needs to be very careful in selecting the Primary Key as an incorrect selection can adversely impact the database architect and future normalization. For a Candidate Key to qualify as a Primary Key, it should be Non-NULL and unique in any domain. I have observed quite often that Primary Keys are seldom changed. I would like to have your feedback on not changing a Primary Key. Create Multiple Filegroup For Single Database Why should one create multiple file group for any database and what are the advantages of the same. In this blog post, I explain the same in detail. List All Objects Created on All Filegroups in Database In this blog post we discuss the essential question – “How can I find which object belongs to which filegroup. Is there any way to know this?” 2010 DATE and TIME in SQL Server 2008 When DATE is converted to DATETIME it adds the of midnight. When TIME is converted to DATETIME it adds the date of 1900 and it is something one wants to consider if you are going to run scripts from SQL Server 2008 to earlier version with CONVERT. Disabled Index and Update Statistics If you do not need a nonclustered index, I suggest you to drop it as keeping them disabled is an overhead on your system. This is because every time the statistics are updated for system all the statistics for disabled indexes are also updated. Precision of SMALLDATETIME – A 1 Minute Precision The precision of the datatype SMALLDATETIME is 1 minute. It discards the seconds by rounding up or rounding down any seconds greater than zero. 2011 Getting Columns Headers without Result Data – SET FMTONLY ON SET FMTONLY ON returns only metadata to the client. It can be used to test the format of the response without actually running the query. When this setting is ON the resultset only have headers of the results but no data. Copy Database from Instance to Another Instance – Copy Paste in SQL Server SQL Server has a feature which copy database from one database to another database and it can be automated as well using SSIS. Make sure you have SQL Server Agent Turned on as this feature will create a job. Puzzle – SELECT * vs SELECT COUNT(*) If you have ever wondered SELECT * gives error when executed alone but SELECT COUNT(*) does not. Why? in that case, you should read this blog post. Creating All New Database with Full Recovery Model This blog post is very based on very interesting story where the user wants to do something by default for every single new database created. Model database is a secret weapon which should be used very carefully and with proper evalution. If used carefully this can be a very much beneficiary when we need a newly created database behave in certain fashion. 2012 In year 2012 I had two interesting series ran on the blog. If there is no fun in learning, the learning becomes a burden. For the same reason, I had decided to build a three part quiz around SEQUENCE. The quiz was to identify the next value of the sequence. I encourage all of you to take part in this fun quiz. Guess the Next Value – Puzzle 1 Guess the Next Value – Puzzle 2 Guess the Next Value – Puzzle 3 Can anyone remember their final day of schooling?  This is probably a silly question because – of course you can!  Many people mark this as the most exciting, happiest day of their life.  It marks the end of testing, the end of following rules set by teachers, and the beginning of finally being able to earn money and work in your chosen field. Read five part series on developer training subject Developer Training - Importance and Significance - Part 1 Developer Training – Employee Morals and Ethics – Part 2 Developer Training – Difficult Questions and Alternative Perspective - Part 3 Developer Training – Various Options for Developer Training – Part 4 Developer Training – A Conclusive Summary- Part 5 Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Memory Lane, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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• Developing Schema Compare for Oracle (Part 1)

  - by Simon Cooper

  SQL Compare is one of Red Gate's most successful SQL Server tools; it allows developers and DBAs to compare and synchronize the contents of their databases. Although similar tools exist for Oracle, they are quite noticeably lacking in the usability and stability that SQL Compare is known for in the SQL Server world. We could see a real need for a usable schema comparison tools for Oracle, and so the Schema Compare for Oracle project was born. Over the next few weeks, as we come up to release of v1, I'll be doing a series of posts on the development of Schema Compare for Oracle. For the first post, I thought I would start with the main pitfalls that we stumbled across when developing the product, especially from a SQL Server background. 1. Schemas and Databases The most obvious difference is that the concept of a 'database' is quite different between Oracle and SQL Server. On SQL Server, one server instance has multiple databases, each with separate schemas. There is typically little communication between separate databases, and most databases are no more than about 1000-2000 objects. This means SQL Compare can register an entire database in a reasonable amount of time, and cross-database dependencies probably won't be an issue. It is a quite different scene under Oracle, however. The terms 'database' and 'instance' are used interchangeably, (although technically 'database' refers to the datafiles on disk, and 'instance' the running Oracle process that reads & writes to the database), and a database is a single conceptual entity. This immediately presents problems, as it is infeasible to register an entire database as we do in SQL Compare; in my Oracle install, using the standard recommended options, there are 63975 system objects. If we tried to register all those, not only would it take hours, but the client would probably run out of memory before we finished. As a result, we had to allow people to specify what schemas they wanted to register. This decision had quite a few knock-on effects for the design, which I will cover in a future post. 2. Connecting to Oracle The next obvious difference is in actually connecting to Oracle – in SQL Server, you can specify a server and database, and off you go. On Oracle things are slightly more complicated. SIDs, Service Names, and TNS A database (the files on disk) must have a unique identifier for the databases on the system, called the SID. It also has a global database name, which consists of a name (which doesn't have to match the SID) and a domain. Alternatively, you can identify a database using a service name, which normally has a 1-to-1 relationship with instances, but may not if, for example, using RAC (Real Application Clusters) for redundancy and failover. You specify the computer and instance you want to connect to using TNS (Transparent Network Substrate). The user-visible parts are a config file (tnsnames.ora) on the client machine that specifies how to connect to an instance. For example, the entry for one of my test instances is: SC_11GDB1 = (DESCRIPTION = (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = simonctest)(PORT = 1521)) ) (CONNECT_DATA = (SID = 11gR1db1) ) ) This gives the hostname, port, and SID of the instance I want to connect to, and associates it with a name (SC_11GDB1). The tnsnames syntax also allows you to specify failover, multiple descriptions and address lists, and client load balancing. You can then specify this TNS identifier as the data source in a connection string. Although using ODP.NET (the .NET dlls provided by Oracle) was fine for internal prototype builds, once we released the EAP we discovered that this simply wasn't an acceptable solution for installs on other people's machines. Due to .NET assembly strong naming, users had to have installed on their machines the exact same version of the ODP.NET dlls as we had on our build server. We couldn't ship the ODP.NET dlls with our installer as the Oracle license agreement prohibited this, and we didn't want to force users to install another Oracle client just so they can run our program. To be able to list the TNS entries in the connection dialog, we also had to locate and parse the tnsnames.ora file, which was complicated by users with several Oracle client installs and intricate TNS entries. After much swearing at our computers, we eventually decided to use a third party Oracle connection library from Devart that we could ship with our program; this could use whatever client version was installed, parse the TNS entries for us, and also had the nice feature of being able to connect to an Oracle server without having any client installed at all. Unfortunately, their current license agreement prevents us from shipping an Oracle SDK, but that's a bridge we'll cross when we get to it. 3. Running synchronization scripts The most important difference is that in Oracle, DDL is non-transactional; you cannot rollback DDL statements like you can on SQL Server. Although we considered various solutions to this, including using the flashback archive or recycle bin, or generating an undo script, no reliable method of completely undoing a half-executed sync script has yet been found; so in this case we simply have to trust that the DBA or developer will check and verify the script before running it. However, before we got to that stage, we had to get the scripts to run in the first place... To run a synchronization script from SQL Compare we essentially pass the script over to the SqlCommand.ExecuteNonQuery method. However, when we tried to do the same for an OracleConnection we got a very strange error – 'ORA-00911: invalid character', even when running the most basic CREATE TABLE command. After much hair-pulling and Googling, we discovered that Oracle has got some very strange behaviour with semicolons at the end of statements. To understand what's going on, we need to take a quick foray into SQL and PL/SQL. PL/SQL is not T-SQL In SQL Server, T-SQL is the language used to interface with the database. It has DDL, DML, control flow, and many other nice features (like Turing-completeness) that you can mix and match in the same script. In Oracle, DDL SQL and PL/SQL are two completely separate languages, with different syntax, different datatypes and different execution engines within the instance. Oracle SQL is much more like 'pure' ANSI SQL, with no state, no control flow, and only the basic DML commands. PL/SQL is the Turing-complete language, but can only do DML and DCL (i.e. BEGIN TRANSATION commands). Any DDL or SQL commands that aren't recognised by the PL/SQL engine have to be passed back to the SQL engine via an EXECUTE IMMEDIATE command. In PL/SQL, a semicolons is a valid token used to delimit the end of a statement. In SQL, a semicolon is not a valid token (even though the Oracle documentation gives them at the end of the syntax diagrams) . When you execute the command CREATE TABLE table1 (COL1 NUMBER); in SQL*Plus the semicolon on the end is a command to SQL*Plus to execute the preceding statement on the server; it strips off the semicolon before passing it on. SQL Developer does a similar thing. When executing a PL/SQL block, however, the syntax is like so: BEGIN INSERT INTO table1 VALUES (1); INSERT INTO table1 VALUES (2); END; / In this case, the semicolon is accepted by the PL/SQL engine as a statement delimiter, and instead the / is the command to SQL*Plus to execute the current block. This explains the ORA-00911 error we got when trying to run the CREATE TABLE command – the server is complaining about the semicolon on the end. This also means that there is no SQL syntax to execute more than one DDL command in the same OracleCommand. Therefore, we would have to do a round-trip to the server for every command we want to execute. Obviously, this would cause lots of network traffic and be very slow on slow or congested networks. Our first attempt at a solution was to wrap every SQL statement (without semicolon) inside an EXECUTE IMMEDIATE command in a PL/SQL block and pass that to the server to execute. One downside of this solution is that we get no feedback as to how the script execution is going; we're currently evaluating better solutions to this thorny issue. Next up: Dependencies; how we solved the problem of being unable to register the entire database, and the knock-on effects to the whole product.

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• Resolving data redundancy up front

  - by okeofs

  Introduction As all of us do when confronted with a problem, the resource of choice is to ‘Google it’. This is where the plot thickens. Recently I was asked to stage data from numerous databases which were to be loaded into a data warehouse. To make a long story short, I was looking for a manner in which to obtain the table names from each database, to ascertain potential overlap.   As the source data comes from a SQL database created from dumps of a third party product,  one could say that there were +/- 95 tables for each database.   Yes I know that first instinct is to use the system stored procedure “exec sp_msforeachdb 'select "?" AS db, * from [?].sys.tables'”. However, if one stops to think about this, it would be nice to have all the results in a temporary or disc based  table; which in itself , implies additional labour. This said,  I decided to ‘re-invent’ the wheel. The full code sample may be found at the bottom of this article.   Define a few temporary tables and variables   declare @SQL varchar(max); declare @databasename varchar(75) /* drop table ##rawdata3 drop table #rawdata1 drop table #rawdata11 */ -- A temp table to hold the names of my databases CREATE TABLE #rawdata1 (    database_name varchar(50) ,    database_size varchar(50),    remarks Varchar(50) )     --A temp table with the same database names as above, HOWEVER using an --Identity number (recNO) as a loop variable. --You will note below that I loop through until I reach 25 (see below) as at --that point the system databases, the reporting server database etc begin. --1- 24 are user databases. These are really what I was looking for. --Whilst NOT the best solution,it works and the code was meant as a quick --and dirty. CREATE TABLE #rawdata11 (    recNo int identity(1,1),    database_name varchar(50) ,    database_size varchar(50),    remarks Varchar(50) )   --My output table showing the database name and table name CREATE TABLE ##rawdata3 (    database_name varchar(75) ,    table_name varchar(75), )   Insert the database names into a temporary table I pull the database names using the system stored procedure sp_databases   INSERT INTO #rawdata1 EXEC sp_databases Go   Insert the results from #rawdata1 into a table containing a record number  #rawdata11 so that I can LOOP through the extract   INSERT into #rawdata11 select * from  #rawdata1   We now declare 3 more variables:  @kounter is used to keep track of our position within the loop. @databasename is used to keep track of the’ current ‘ database name being used in the current pass of the loop;  as inorder to obtain the tables for that database we  need to issue a ‘USE’ statement, an insert command and other related code parts. This is the challenging part. @sql is a varchar(max) variable used to contain the ‘USE’ statement PLUS the’ insert ‘ code statements. We now initalize @kounter to 1 .   declare @kounter int; declare @databasename varchar(75); declare @sql varchar(max); set @kounter = 1   The Loop The astute reader will remember that the temporary table #rawdata11 contains our  database names  and each ‘database row’ has a record number (recNo). I am only interested in record numbers under 25. I now set the value of the temporary variable @DatabaseName (see below) .Note that I used the row number as a part of the predicate. Now, knowing the database name, I can create dynamic T-SQL to be executed using the sp_sqlexec stored procedure (see the code in red below). Finally, after all the tables for that given database have been placed in temporary table ##rawdata3, I increment the counter and continue on. Note that I used a global temporary table to ensure that the result set persists after the termination of the run. At some stage, I plan to redo this part of the code, as global temporary tables are not really an ideal solution.    WHILE (@kounter < 25)  BEGIN  select @DatabaseName = database_name from #rawdata11 where recNo = @kounter  set @SQL = 'Use ' + @DatabaseName + ' Insert into ##rawdata3 ' + + ' SELECT table_catalog,Table_name FROM information_schema.tables' exec sp_sqlexec  @Sql  SET @kounter  = @kounter + 1  END   The full code extract   Here is the full code sample.   declare @SQL varchar(max); declare @databasename varchar(75) /* drop table ##rawdata3 drop table #rawdata1 drop table #rawdata11 */ CREATE TABLE #rawdata1 (    database_name varchar(50) ,    database_size varchar(50),    remarks Varchar(50) ) CREATE TABLE #rawdata11 (    recNo int identity(1,1),    database_name varchar(50) ,    database_size varchar(50),    remarks Varchar(50) ) CREATE TABLE ##rawdata3 (    database_name varchar(75) ,    table_name varchar(75), )   INSERT INTO #rawdata1 EXEC sp_databases go INSERT into #rawdata11 select * from  #rawdata1 declare @kounter int; declare @databasename varchar(75); declare @sql varchar(max); set @kounter = 1 WHILE (@kounter < 25)  BEGIN  select @databasename = database_name from #rawdata11 where recNo = @kounter  set @SQL = 'Use ' + @DatabaseName + ' Insert into ##rawdata3 ' + + ' SELECT table_catalog,Table_name FROM information_schema.tables' exec sp_sqlexec  @Sql  SET @kounter  = @kounter + 1  END    select * from ##rawdata3  where table_name like '%SalesOrderHeader%'

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• ?11.2RAC??????????????

  - by JaneZhang(???)

         ?????,???????????????,???dbca???????,???????????dbca,?????????11.2???????,???????,??dbca??????????????????,????????????????     ????11.2???????RACDB2???,?????RACDB1? ?????rac1,????rac2?     ?11.2?,?????grid?????GI,??oracle????????,????????oracle?????? 1. ??????????????????,?????,???????????:audit_file_dest, background_dump_dest, user_dump_dest ?core_dump_dest????audit_file_dest=/u01/app/oracle/admin/RACDB/adump,?????????,?????????:ORA-09925: Unable to create audit trail fileLinux-x86_64 Error: 2: No such file or directoryAdditional information: 99252. ????????????????????????????:SQL> alter system set instance_number=2 scope=spfile sid='RACDB2';SQL> alter system set thread=2 scope=spfile sid='RACDB2';SQL> alter system set undo_tablespace='UNDOTBS2' scope=spfile sid='RACDB2';SQL> alter system set local_listener='(DESCRIPTION=(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=192.0.2.122)(PORT=1521))))' sid='RACDB2'; <=====192.0.2.122???2?VIP 3. ???????DB?$ORACLE_HOME/dbs/init<sid>.ora ?????DB?$ORACLE_HOME/dbs/init<sid>.ora,??????????????init<sid>.ora ????,????spfile???:=======================SPFILE='+DATA/racdb/spfileracdb.ora'??:[oracle@rac1 ~]$ scp $ORACLE_HOME/dbs/initRACDB1.ora rac2:$ORACLE_HOME/dbs/initRACDB2.ora <===????????24.  ??????/etc/oratab,????????????:RACDB2:/u01/app/oracle/product/11.2.0/dbhome_1:N       5.  ???????????: DB?$ORACLE_HOME/dbs/ora<sid>.pwd ????DB?$ORACLE_HOME/dbs/ora<sid>.pwd,??????????????:[oracle@rac1 dbs]$ scp $ORACLE_HOME/dbs/orapwRACDB1 rac2:$ORACLE_HOME/dbs/orapwRACDB2 <==?????26.  ?????????????,????????UNDO TABLESPACE?(??????dbca?????,???????undo tablespace????,?????????)??:SQL>CREATE UNDO TABLESPACE "UNDOTBS2" DATAFILE '/dev/….' SIZE 4096M ;???????:SQL>CREATE UNDO TABLESPACE "UNDOTBS2" DATAFILE '+DATA' SIZE 4096M ;7.  ?????????????,????????redo thread?redo log:??:SQL> alter database add logfile thread 2      group 3 ('/dev/...', '/dev/...') size 1024M,     group 4 ('/dev/...','dev/...') size 1024M;???????:SQL> alter database add logfile thread 2     group 3 ('+DATA','+RECO') size 1024M,     group 4 ('+DATA','+RECO') size 1024M;SQL> alter database enable thread 2; <==????thread8.  ??????????,?????????????:[oracle@rac2 admin]$su - oracle[oracle@rac2 admin]$export ORACLE_HOME=/u01/app/oracle/product/11.2.0/dbhome_1[oracle@rac2 admin]$export ORACLE_SID=RACDB2[oracle@rac2 admin]$ sqlplus / as sysdbaSQL> startup <==??????,???????2????????????9. ?????OCR???GI??,?????????????:$srvctl add instance -d <database name> -i <new instance name> -n <new node name>Example of srvctl add instance command:============================[oracle@rac2 ~]$ srvctl add instance -d racdb -i RACDB2 -n rac2  <==????????,????ps -ef|grep smon???[oracle@rac2 dbs]$ ps -ef|grep smonroot      3453     1  1 Jun12 ?        04:03:05 /u01/app/11.2.0/grid/bin/osysmond.bingrid      3727     1  0 Jun12 ?        00:00:19 asm_smon_+ASM2oracle    5343  4543  0 14:06 pts/1    00:00:00 grep smonoracle   28736     1  0 Jun25 ?        00:00:03 ora_smon_RACDB2 <========??????10. ???????:$su - grid[grid@rac2 ~]$ crsctl stat res -t...ora.racdb.db      1        ONLINE  ONLINE       rac1                     Open                      2        OFFLINE OFFLINE             rac2????,??????offline,????????????sqlplus??????sqlplus??????,???srvctl??:[grid@rac2 ~]$ su  - oraclePassword: [oracle@rac2 ~]$ sqlplus / as sysdbaSQL> shutdown immediate;Database closed.Database dismounted.ORACLE instance shut down.SQL> exit[oracle@rac2 ~]$ srvctl start instance -d racdb -i RACDB2[oracle@rac2 ~]$ su - gridPassword: [grid@rac2 ~]$ crsctl stat res -tora.racdb.db      1        ONLINE  ONLINE       rac1                     Open                      2        ONLINE  ONLINE       rac2                     Open                11. ?????????:[oracle@rac2 ~]$ crsctl stat res ora.racdb.db -pNAME=ora.racdb.dbTYPE=ora.database.typeACL=owner:oracle:rwx,pgrp:oinstall:rwx,other::r--ACTION_FAILURE_TEMPLATE=ACTION_SCRIPT=ACTIVE_PLACEMENT=1AGENT_FILENAME=%CRS_HOME%/bin/oraagent%CRS_EXE_SUFFIX%AUTO_START=restoreCARDINALITY=2CHECK_INTERVAL=1CHECK_TIMEOUT=30CLUSTER_DATABASE=trueDATABASE_TYPE=RACDB_UNIQUE_NAME=RACDBDEFAULT_TEMPLATE=PROPERTY(RESOURCE_CLASS=database) PROPERTY(DB_UNIQUE_NAME= CONCAT(PARSE(%NAME%, ., 2), %USR_ORA_DOMAIN%, .)) ELEMENT(INSTANCE_NAME= %GEN_USR_ORA_INST_NAME%) ELEMENT(DATABASE_TYPE= %DATABASE_TYPE%)DEGREE=1DESCRIPTION=Oracle Database resourceENABLED=1FAILOVER_DELAY=0FAILURE_INTERVAL=60FAILURE_THRESHOLD=1GEN_AUDIT_FILE_DEST=/u01/app/oracle/admin/RACDB/adumpGEN_START_OPTIONS=GEN_START_OPTIONS@SERVERNAME(rac1)=openGEN_START_OPTIONS@SERVERNAME(rac2)=openGEN_USR_ORA_INST_NAME=GEN_USR_ORA_INST_NAME@SERVERNAME(rac1)=RACDB1HOSTING_MEMBERS=INSTANCE_FAILOVER=0LOAD=1LOGGING_LEVEL=1MANAGEMENT_POLICY=AUTOMATICNLS_LANG=NOT_RESTARTING_TEMPLATE=OFFLINE_CHECK_INTERVAL=0ONLINE_RELOCATION_TIMEOUT=0ORACLE_HOME=/u01/app/oracle/product/11.2.0/dbhome_1ORACLE_HOME_OLD=PLACEMENT=restrictedPROFILE_CHANGE_TEMPLATE=RESTART_ATTEMPTS=2ROLE=PRIMARYSCRIPT_TIMEOUT=60SERVER_POOLS=ora.RACDBSPFILE=+DATA/RACDB/spfileRACDB.oraSTART_DEPENDENCIES=hard(ora.DATA.dg,ora.RECO.dg) weak(type:ora.listener.type,global:type:ora.scan_listener.type,uniform:ora.ons,global:ora.gns) pullup(ora.DATA.dg,ora.RECO.dg)START_TIMEOUT=600STATE_CHANGE_TEMPLATE=STOP_DEPENDENCIES=hard(intermediate:ora.asm,shutdown:ora.DATA.dg,shutdown:ora.RECO.dg)STOP_TIMEOUT=600TYPE_VERSION=3.2UPTIME_THRESHOLD=1hUSR_ORA_DB_NAME=RACDBUSR_ORA_DOMAIN=USR_ORA_ENV=USR_ORA_FLAGS=USR_ORA_INST_NAME=USR_ORA_INST_NAME@SERVERNAME(rac1)=RACDB1USR_ORA_INST_NAME@SERVERNAME(rac2)=RACDB2USR_ORA_OPEN_MODE=openUSR_ORA_OPI=falseUSR_ORA_STOP_MODE=immediateVERSION=11.2.0.3.0???11.2,?OCR???database??,??????,???????????database???????database???????,??????,???????????????ASM????????????  ?:dbca ???????????:????????oracle????dbca:su - oracledbca?? RAC database?? Instance Management?? add an instance???active rac database??????? ??undo?redo??

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• CQRS &ndash; Questions and Concerns

  - by Dylan Smith

  I’ve been doing a lot of learning on CQRS and Event Sourcing over the last little while and I have a number of questions that I haven’t been able to answer. 1. What is the benefit of CQRS when compared to a typical DDD architecture that uses Event Sourcing and properly captures intent and behavior via verb-based commands? (other than Scalability) 2. When using CQRS what do you do with complex query-based logic? I’m going to elaborate on #1 in this blog post and I’ll do a follow-up post on #2. I watched through Greg Young’s video on the business benefits of CQRS + Event Sourcing and first let me say that I thought it was an excellent presentation that really drives home a lot of the benefits to this approach to architecture (I watched it twice in a row I enjoyed it so much!). But it didn’t answer some of my questions fully (I wish I had been there to ask these of Greg in person!). So let me pick apart some of the points he makes and how they relate to my first question above. I’m completely sold on the idea of event sourcing and have a clear understanding of the benefits that it brings to the table, so I’m not going to question that. But you can use event sourcing without going to a CQRS architecture, so my main question is around the benefits of CQRS + Event Sourcing vs Event Sourcing + Typical DDD architecture Architecture with Event Sourcing + Commands on Left, CQRS on Right Greg talks about how the stereotypical architecture doesn’t support DDD, but is that only because his diagram shows DTO’s coming up from the client. If we use the same diagram but allow the client to send commands doesn’t that remove a lot of the arguments that Greg makes against the stereotypical architecture? We can now introduce verbs into the system. We can capture intent now (storing it still requires event sourcing, but you can implement event sourcing without doing CQRS) We can create a rich domain model (as opposed to an anemic domain model) Scalability is obviously a benefit that CQRS brings to the table, but like Greg says, very few of the systems we create truly need significant scalability Greg talks about the ability to scale your development efforts. He says CQRS allows you to split the system into 3 parts (Client, Domain/Commands, Reads) and assign 3 teams of developers to work on them in parallel; letting you scale your development efforts by 3x with nearly linear gains. But in the stereotypical architecture don’t you already have 2 separate modules that you can split your dev efforts between: The client that sends commands/queries and receives DTO’s, and the Domain which accepts commands/queries, and generates events/DTO’s. If this is true it’s not really a 3x scaling you achieve with CQRS but merely a 1.5x scaling which while great doesn’t sound nearly as dramatic (“I can do it with 10 devs in 12 months – let me hire 5 more and we can have it done in 8 months”). Making the Query side “stupid simple” such that you can assign junior developers (or even outsource it) sounds like a valid benefit, but I have some concerns over what you do with complex query-based logic/behavior. I’m going to go into more detail on this in a follow-up blog post shortly. He also seemed to focus on how “stupid-simple” it is doing queries against the de-normalized data store, but I imagine there is still significant complexity in the event handlers that interpret the events and apply them to the de-normalized tables. It sounds like Greg suggests that because we’re doing CQRS that allows us to apply Event Sourcing when we otherwise wouldn’t be able to (~33:30 in the video). I don’t believe this is true. I don’t see why you wouldn’t be able to apply Event Sourcing without separating out the Commands and Queries. The queries would just operate against the domain model instead of the database. But you’d still get the benefits of Event Sourcing. Without CQRS the queries would only be able to operate against the current state rather than the event history, but even in CQRS the domain behaviors can only operate against the current state and I don’t see that being a big limiting factor. If some query needs to operate against something that is not captured by the current state you would just have to update the domain model to capture that information (no different than if that statement were made about a Command under CQRS). Some of the benefits I do see being applicable are that your domain model might end up being simpler/smaller since it only needs to represent the state needed to process commands and not worry about the reads (like the Deactivate Inventory Item and associated comment example that Greg provides). And also commands that can be handled in a Transaction Script style manner by the command handler simply generating events and not touching the domain model. It also makes it easier for your senior developers to focus on the command behavior and ignore the queries, which is usually going to be a better use of their time. And of course scalability. If anybody out there has any thoughts on this and can help educate me further, please either leave a comment or feel free to get in touch with me via email:

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• Connection Pooling is Busted

  - by MightyZot

  A few weeks ago we started getting complaints about performance in an application that has performed very well for many years.  The application is a n-tier application that uses ADODB with the SQLOLEDB provider to talk to a SQL Server database.  Our object model is written in such a way that each public method validates security before performing requested actions, so there is a significant number of queries executed to get information about file cabinets, retrieve images, create workflows, etc.  (PaperWise is a document management and workflow system.)  A common factor for these customers is that they have remote offices connected via MPLS networks. Naturally, the first thing we looked at was the query performance in SQL Profiler.  All of the queries were executing within expected timeframes, most of them were so fast that the duration in SQL Profiler was zero.  After getting nowhere with SQL Profiler, the situation was escalated to me.  I decided to take a peek with Process Monitor.  Procmon revealed some “gaps” in the TCP/IP traffic.  There were notable delays between send and receive pairs.  The send and receive pairs themselves were quite snappy, but quite often there was a notable delay between a receive and the next send.  You might expect some delay because, presumably, the application is doing some thinking in-between the pairs.  But, comparing the procmon data at the remote locations with the procmon data for workstations on the local network showed that the remote workstations were significantly delayed.  Procmon also showed a high number of disconnects. Wireshark traces showed that connections to the database were taking between 75ms and 150ms.  Not only that, but connections to a file share containing images were taking 2 seconds!  So, I asked about a trust.  Sure enough there was a trust between two domains and the file share was on the second domain.  Joining a remote workstation to the domain hosting the share containing images alleviated the time delay in accessing the file share.  Removing the trust had no affect on the connections to the database. Microsoft Network Monitor includes filters that parse TDS packets.  TDS is the protocol that SQL Server uses to communicate.  There is a certificate exchange and some SSL that occurs during authentication.  All of this was evident in the network traffic.  After staring at the network traffic for a while, and examining packets, I decided to call it a night.  On the way home that night, something about the traffic kept nagging at me.  Then it dawned on me…at the beginning of the dance of packets between the client and the server all was well.  Connection pooling was working and I could see multiple queries getting executed on the same connection and ethereal port.  After a particular query, connecting to two different servers, I noticed that ADODB and SQLOLEDB started making repeated connections to the database on different ethereal ports.  SQL Server would execute a single query and respond on a port, then open a new port and execute the next query.  Connection pooling appeared to be broken. The next morning I wrote a test to confirm my hypothesis.  Turns out that the sequence causing the connection nastiness goes something like this: Make a connection to the database. Open a result set that returns enough records to require multiple roundtrips to the server. For each result, query for some other data in the database (this will open a new implicit connection.) Close the inner result set and repeat for every item in the original result set. Close the original connection. Provided that the first result set returns enough data to require multiple roundtrips to the server, ADODB and SQLOLEDB will start making new connections to the database for each query executed in the loop.  Originally, I thought this might be due to Microsoft’s denial of service (ddos) attack protection.  After turning those features off to no avail, I eventually thought to switch my queries to client-side cursors instead of server-side cursors.  Server-side cursors are the default, by the way.  Voila!  After switching to client-side cursors, the disconnects were gone and the above sequence yielded two connections as expected. While the real problem is the amount of time it takes to make connections over these MPLS networks (100ms on average), switching to client-side cursors made the problem go away.  Believe it or not, this is actually documented by Microsoft, and rather difficult to find.  (At least it was while we were trying to troubleshoot the problem!)  So, if you’re noticing performance issues on slower networks, or networks with slower switching, take a look at the traffic in a tool like Microsoft Network Monitor.  If you notice a high number of disconnects, and you’re using fire-hose or server-side cursors, then try switching to client-side cursors and you may see the problem go away. Most likely, Microsoft believes this to be appropriate behavior, because ADODB can’t guarantee that all of the data has been retrieved when you execute the inner queries.  I’m not convinced, though, because the problem remains even after replacing all of the implicit connections with explicit connections and closing those connections in-between each of the inner queries.  In that case, there doesn’t seem to be a reason why ADODB can’t use a single connection from the connection pool to make the additional queries, bringing the total number of connections to two.  Instead ADO appears to make an assumption about the state of the connection. I’ve reported the behavior to Microsoft and am awaiting to hear from the appropriate team, so that I can demonstrate the problem.  Maybe they can explain to us why this is appropriate behavior.  :)

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• CQRS - Benefits

  - by Dylan Smith

  Thanks to all the comments and feedback from the last post I think I have a better understanding now of the benefits of CQRS (separate from the benefits of Event Sourcing). I’m going to try and sum it up here, and point out some areas where I could still use some advice: CQRS Benefits Sounds like the primary benefit of CQRS as an architecture is it allows you to create a simpler domain model by sucking out everything related to queries. I can definitely see the benefit to this, in general the domain logic related to commands is the high-value behavior in the software, but the logic required to service the queries would add a lot of low-value “noise” to the domain model that would dilute the high-value (command) behavior – sorting, paging, filtering, pre-fetch paths, etc. Also the most appropriate domain structure for implementing commands might not be the most optimal for implementing queries. To paraphrase Greg, this usually results in a domain model that is mediocre at both, piss-poor at one, or more likely piss-poor at both commands and queries. Not only will you be able to simplify your domain model by pulling out all the query logic, but at least a handful of commands in most systems will probably be “pass-though” type commands with little to no logic that just generate events. If these can be implemented directly in the command-handler and never touch the domain model, this allows you to slim down the domain model even more. Also, if you were to do event sourcing without CQRS, you no longer have a database containing the current state (only the domain model would) which makes it difficult (or impossible) to support ad-hoc querying and/or reporting that is common in most business software. Of course CQRS provides some great scalability benefits, not only scalability but I have to assume that it provides extremely low latency for most operations, especially if you have an asynchronous event bus. I know Greg says that you get a 3x scaling (Commands, Queries, Client) of your ability to perform parallel development, but IMHO, it seems like it only provides 1.5x scaling since even without CQRS you’re going to have your client loosely coupled to your domain - which is still a great benefit to be able to realize. Questions / Concerns If all the queries against an aggregate get pulled out to the Query layer, what if the only commands for that aggregate can be handled in a “pass-through” manner with the command handler directly generating events. Is it possible to have an aggregate that isn’t modeled in the domain model? Are there any issues or downsides to this? I know in the feedback from my previous posts it was suggested that having one domain model handling both commands and queries requires implementing a lot of traversals between objects that wouldn’t be necessary if it was only servicing commands. My question is, do you include traversals in your domain model based on the needs of the code, or based on the conceptual domain model? If none of my Commands require a Customer.Orders traversal, but the conceptual domain includes the concept of a set of orders belonging to a customer – should I model that in my domain model or not? I like the idea of using the Query side of the architecture as a place to put junior devs where the risk of them screwing something up has minimal impact. But I’m not sold on the idea that you can actually outsource it. Like I said in one of my comments on my previous post, the code to handle a query and generate DTO’s is going to be dead simple, but the code to process events and apply them to the tables on the query side is going to require a significant amount of domain knowledge to know which events to listen for to update each of the de-normalized tables (and what changes need to be made when each event is processed). I don’t know about everybody else, but having Indian/Russian/whatever outsourced developers have to do anything that requires significant domain knowledge has never been successful in my experience. And if you need to spec out for each new query which events to listen to and what to do with each one, well that’s probably going to be just as much work to document as it would be to just implement it. Greg made the point in a comment that doing an aggregate query like “Total Sales By Customer” is going to be inefficient if you use event sourcing but not CQRS. I don’t understand why that would be the case. I imagine in that case you’d simply have a method/property on the Customer object that calculated total sales for that customer by enumerating over the Orders collection. Then the application services layer would generate DTO’s off of the Customers collection that included say the CustomerID, CustomerName, TotalSales, or whatever the case may be. As long as you use a snapshotting implementation, I don’t see why that would be anymore inefficient in a DDD+Event Sourcing implementation than in a typical DDD implementation. Like I mentioned in my last post I still have some questions about query logic that haven’t been answered yet, but before I start asking those I want to make sure I have a strong grasp on what benefits CQRS provides.  My main concern with the query logic was that I know I could just toss it all into the query side, but I was concerned that I would be losing the benefits of using CQRS in the first place if I did that.  I want to elaborate more on this though with some example situations in an upcoming post.

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• Columnstore Case Study #2: Columnstore faster than SSAS Cube at DevCon Security

  - by aspiringgeek

  Preamble This is the second in a series of posts documenting big wins encountered using columnstore indexes in SQL Server 2012 & 2014.  Many of these can be found in my big deck along with details such as internals, best practices, caveats, etc.  The purpose of sharing the case studies in this context is to provide an easy-to-consume quick-reference alternative. See also Columnstore Case Study #1: MSIT SONAR Aggregations Why Columnstore? As stated previously, If we’re looking for a subset of columns from one or a few rows, given the right indexes, SQL Server can do a superlative job of providing an answer. If we’re asking a question which by design needs to hit lots of rows—DW, reporting, aggregations, grouping, scans, etc., SQL Server has never had a good mechanism—until columnstore. Columnstore indexes were introduced in SQL Server 2012. However, they're still largely unknown. Some adoption blockers existed; yet columnstore was nonetheless a game changer for many apps.  In SQL Server 2014, potential blockers have been largely removed & they're going to profoundly change the way we interact with our data.  The purpose of this series is to share the performance benefits of columnstore & documenting columnstore is a compelling reason to upgrade to SQL Server 2014. The Customer DevCon Security provides home & business security services & has been in business for 135 years. I met DevCon personnel while speaking to the Utah County SQL User Group on 20 February 2012. (Thanks to TJ Belt (b|@tjaybelt) & Ben Miller (b|@DBADuck) for the invitation which serendipitously coincided with the height of ski season.) The App: DevCon Security Reporting: Optimized & Ad Hoc Queries DevCon users interrogate a SQL Server 2012 Analysis Services cube via SSRS. In addition, the SQL Server 2012 relational back end is the target of ad hoc queries; this DW back end is refreshed nightly during a brief maintenance window via conventional table partition switching. SSRS, SSAS, & MDX Conventional relational structures were unable to provide adequate performance for user interaction for the SSRS reports. An SSAS solution was implemented requiring personnel to ramp up technically, including learning enough MDX to satisfy requirements. Ad Hoc Queries Even though the fact table is relatively small—only 22 million rows & 33GB—the table was a typical DW table in terms of its width: 137 columns, any of which could be the target of ad hoc interrogation. As is common in DW reporting scenarios such as this, it is often nearly to optimize for such queries using conventional indexing. DevCon DBAs & developers attended PASS 2012 & were introduced to the marvels of columnstore in a session presented by Klaus Aschenbrenner (b|@Aschenbrenner) The Details Classic vs. columnstore before-&-after metrics are impressive. Scenario Conventional Structures Columnstore ? SSRS via SSAS 10 - 12 seconds 1 second >10x Ad Hoc 5-7 minutes (300 - 420 seconds) 1 - 2 seconds >100x Here are two charts characterizing this data graphically.  The first is a linear representation of Report Duration (in seconds) for Conventional Structures vs. Columnstore Indexes.  As is so often the case when we chart such significant deltas, the linear scale doesn’t expose some the dramatically improved values corresponding to the columnstore metrics.  Just to make it fair here’s the same data represented logarithmically; yet even here the values corresponding to 1 –2 seconds aren’t visible.  The Wins Performance: Even prior to columnstore implementation, at 10 - 12 seconds canned report performance against the SSAS cube was tolerable. Yet the 1 second performance afterward is clearly better. As significant as that is, imagine the user experience re: ad hoc interrogation. The difference between several minutes vs. one or two seconds is a game changer, literally changing the way users interact with their data—no mental context switching, no wondering when the results will appear, no preoccupation with the spinning mind-numbing hurry-up-&-wait indicators.  As we’ve commonly found elsewhere, columnstore indexes here provided performance improvements of one, two, or more orders of magnitude. Simplified Infrastructure: Because in this case a nonclustered columnstore index on a conventional DW table was faster than an Analysis Services cube, the entire SSAS infrastructure was rendered superfluous & was retired. PASS Rocks: Once again, the value of attending PASS is proven out. The trip to Charlotte combined with eager & enquiring minds let directly to this success story. Find out more about the next PASS Summit here, hosted this year in Seattle on November 4 - 7, 2014. DevCon BI Team Lead Nathan Allan provided this unsolicited feedback: “What we found was pretty awesome. It has been a game changer for us in terms of the flexibility we can offer people that would like to get to the data in different ways.” Summary For DW, reports, & other BI workloads, columnstore often provides significant performance enhancements relative to conventional indexing.  I have documented here, the second in a series of reports on columnstore implementations, results from DevCon Security, a live customer production app for which performance increased by factors of from 10x to 100x for all report queries, including canned queries as well as reducing time for results for ad hoc queries from 5 - 7 minutes to 1 - 2 seconds. As a result of columnstore performance, the customer retired their SSAS infrastructure. I invite you to consider leveraging columnstore in your own environment. Let me know if you have any questions.

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• issue in list of dict

  - by gaggina

  class MyOwnClass: # list who contains the queries queries = [] # a template dict template_query = {} template_query['name'] = 'mat' template_query['age'] = '12' obj = MyOwnClass() query = obj.template_query query['name'] = 'sam' query['age'] = '23' obj.queries.append(query) query2 = obj.template_query query2['name'] = 'dj' query2['age'] = '19' obj.queries.append(query2) print obj.queries It gives me [{'age': '19', 'name': 'dj'}, {'age': '19', 'name': 'dj'}] while I expect to have [{'age': '23' , 'name': 'sam'}, {'age': '19', 'name': 'dj'}] I thought to use a template for this list because I'm gonna to use it very often and there are some default variable who does not need to be changed. Why does doing it the template_query itself changes? I'm new to python and I'm getting pretty confused.

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• JDBC query to Oracle

  - by Harish

  Hi, We are planning to migrate our DB to Oracle.We need to manually check each of the embedded SQL is working in Oracle as few may follow different SQL rules.Now my need is very simple. I need to browse through a file which may contain queries like this. String sql = "select * from test where name="+test+"and age="+age; There are nearly 1000 files and each file has different kind of queries like this where I have to pluck the query alone which I have done through an unix script.But I need to convert these Java based queries to Oracle compatible queries. ie. select * from test where name="name" and age="age" Basically I need to check the syntax of the queries by this.I have seen something like this in TOAD but I have more than 1000 files and can't manually change each one.Is there a way? I will explain more i the question is not clear

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• Would a Socket Connection Outperform an Intarvaled Database Sweep and Requests?

  - by Jascha

  I'm building a small chat application to add to an existing framework. There will only be 20-50 users MAX at any one time. I was wondering if I could get away with updating a cache file containing (semi) live chat data for whichever users happen to be chatting just by performing timed queries and regular AJAX refreshes for new data as opposed to learning how to open and maintain a socket connection. I'm sure there are existing chat plug-ins out there. But I just had a hell of a time installing one and I could see building the whole damn thing taking just as much time as plugging one in. Am I off to a bad start? Thanks in advance -J (p.s. this is a semi closed network behind a php login so security isn't a great concern)

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• Performance - User defined query / filter to search data

  - by Cagatay Kalan

  What is the best way to design a system where users can create their own criterias to search data ? By "design" i mean, data storage, data access layer and search structure. We will actually refactor an existing application which is written in C# and ASP .NET and we don't want to change the infrastructure. Our main issue is performance and we use MSSQL and DevExpress to build queries. Some queries run in 4-5 minutes and all the columns included in the queries have indexes. When i check queries, i see that DevExpress builds too many "exists" clauses and i'm not happy with that because i have doubts that some of these queries skip some indexes. What may be the alternatives to DevExpress? NHibernate or Entity Framework? Can we build dynamic criteria system and store these to database in both of them ? And also do we need any alternative storage like a lucene index or OLAP database?

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• is there a tool to see the difference between two database tables in SQL Server?

  - by reinier

  What is a good tool to see the differences between 2 tables (or even better, the datasets returned by 2 queries). EDIT: I'm not interested in the schema changes. Just assume that the schemas are the same. background as to why: I'm porting some legacy code which can fill a database with some pre-calced data. The easiest way to see if I got everything right, is to check the output of the old program, with the new one. I was thinking that if there is some kind of 'diff' tool for databases, this might be great.

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• is there a tool to see the difference between two database tables in mssql?

  - by reinier

  What is a good tool to see the differences between 2 tables (or even better, the datasets returned by 2 queries). EDIT: I'm not interested in the schema changes. Just assume that the schemas are the same. background as to why: I'm porting some legacy code which can fill a database with some pre-calced data. The easiest way to see if I got everything right, is to check the output of the old program, with the new one. I was thinking that if there is some kind of 'diff' tool for databases, this might be great.

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• How do you optimize database performance when providing results for autocomplete/iterative search?

  - by Howiecamp

  Note: In this question I'm using the term "autocomplete" (or "iterative search") to refer to returning search-as-you-type results, e.g. like Google Search gives you. Also my question is not specific to web applications vs. fat client apps. How are SQL SELECT queries normally constructed to provide decent performance for this type of query, especially over arbitrarily large data sets? In the case where the search will only query based on the first n characters (easiest case) am I still issuing a new SELECT result FROM sometable WHERE entry LIKE... on each keypress. Even with various forms of caching this seems like it might result in poor performance. In cases where you want your search string to return results with prefix matches, substring matches, etc. it's an even more difficult problem. Looking at a case of searching a list of contacts, you might return results that match FirstName + LastName, LastName + FirstName, or any other substring.

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