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• How to use OO for data analysis? [closed]

  - by Konsta

  In which ways could object-orientation (OO) make my data analysis more efficient and let me reuse more of my code? The data analysis can be broken up into get data (from db or csv or similar) transform data (filter, group/pivot, ...) display/plot (graph timeseries, create tables, etc.) I mostly use Python and its Pandas and Matplotlib packages for this besides some DB connectivity (SQL). Almost all of my code is a functional/procedural mix. While I have started to create a data object for a certain collection of time series, I wonder if there are OO design patterns/approaches for other parts of the process that might increase efficiency?

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• Loading XML file containing leading zeros with SSIS preserving the zeros

  - by Compudicted

  Visiting the MSDN SQL Server Integration Services Forum oftentimes I could see that people would pop up asking this question: “why I am not able to load an element from an XML file that contains zeros so the leading/trailing zeros would remain intact?”. I started to suspect that such a trivial and often-required operation perhaps is being misunderstood by the developer community. I would also like to add that the whole state of affairs surrounding the XML today is probably also going to be increasingly affected by a motion of people who dislike XML in general and many aspects of it as XSD and XSLT invoke a negative reaction at best. Nevertheless, XML is in wide use today and its importance as a bridge between diverse systems is ever increasing. Therefore, I deiced to write up an example of loading an arbitrary XML file that contains leading zeros in one of its elements using SSIS so the leading zeros would be preserved keeping in mind the goal on simplicity into a table in SQL Server database. To start off bring up your BIDS (running as admin) and add a new Data Flow Task (DFT). This DFT will serve as container to adding our XML processing elements (besides, the XML Source is not available anywhere else other than from within the DFT). Double-click your DFT and drag and drop the XMS Source component from the Tool Box’s Data Flow Sources. Now, let the fun begin! Being inspired by the upcoming Christmas I created a simple XML file with one set of data that contains an imaginary SSN number of Rudolph containing several leading zeros like 0000003. This file can be viewed here. To configure the XML Source of course it is quite intuitive to point it to our XML file, next what the XML source needs is either an embedded schema (XSD) or it can generate one for us. In lack of the one I opted to auto-generate it for me and I ended up with an XSD that looked like: <?xml version="1.0"?> <xs:schema attributeFormDefault="unqualified" elementFormDefault="qualified" xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="XMasEvent"> <xs:complexType> <xs:sequence> <xs:element minOccurs="0" name="CaseInfo"> <xs:complexType> <xs:sequence> <xs:element minOccurs="0" name="ID" type="xs:unsignedByte" /> <xs:element minOccurs="0" name="CreatedDate" type="xs:unsignedInt" /> <xs:element minOccurs="0" name="LastName" type="xs:string" /> <xs:element minOccurs="0" name="FirstName" type="xs:string" /> <xs:element minOccurs="0" name="SSN" type="xs:unsignedByte" /> <!-- Becomes string -- > <xs:element minOccurs="0" name="DOB" type="xs:unsignedInt" /> <xs:element minOccurs="0" name="Event" type="xs:string" /> <xs:element minOccurs="0" name="ClosedDate" /> </xs:sequence> </xs:complexType> </xs:element> </xs:sequence> </xs:complexType> </xs:element> </xs:schema> As an aside on the XML file: if your XML file does not contain the outer node (<XMasEvent>) then you may end up in a situation where you see just one field in the output. Now please note that the SSN element’s data type was chosen to be of unsignedByte (and this is for a reason). The reason is stemming from the fact all our figures in the element are digits, this is good, but this is not exactly what we need, because if we will attempt to load the data with this XSD then we are going to either get errors on the destination or most typically lose the leading zeros. So the next intuitive choice is to change the data type to string. Besides, if a SSIS package was already created based on this XSD and the data type change was done thereafter, one should re-set the metadata by right-clicking the XML Source and choosing “Advanced Editor” in which there is a refresh button at the bottom left which will do the trick. So far so good, we are ready to load our XML file, well actually yes, and no, in my experience typically some data conversion may be required. So depending on your data destination you may need to tweak the data types targeted. Let’s add a Data Conversion Task to our DFT. Your package should look like: To make the story short I only will cover the SSN field, so in my data source the target SQL Table has it as nchar(10) and we chose string in our XSD (yes, this is a big difference), under such circumstances the SSIS will complain. So will go and manipulate on the data type of SSN by making it Unicode String (DT_WSTR), World String per se. The conversion should look like: The peek at the Metadata: We are almost there, now all we need is to configure the destination. For simplicity I chose SQL Server Destination. The mapping is a breeze, F5 and I am able to insert my data into SQL Server now! Checking the zeros – they are all intact!

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• Enabling EUS support in OUD 11gR2 using command line interface

  - by Sylvain Duloutre

  Enterprise User Security (EUS) allows Oracle Database to use users & roles stored in LDAP for authentication and authorization.Since the 11gR2 release, OUD natively supports EUS. EUS can be easily configured during OUD setup. ODSM (the graphical admin console) can also be used to enable EUS for a new suffix. However, enabling EUS for a new suffix using command line interface is currently not documented, so here is the procedure: Let's assume that EUS support was enabled during initial setup.Let's o=example be the new suffix I want to use to store Enterprise users. The following sequence of command must be applied for each new suffix: // Create a local database holding EUS context infodsconfig create-workflow-element --set base-dn:cn=OracleContext,o=example --set enabled:true --type db-local-backend --element-name exampleContext -n // Add a workflow element in the call path to generate on the fly attributes required by EUSdsconfig create-workflow-element --set enabled:true --type eus-context --element-name eusContext --set next-workflow-element:exampleContext -n // Add the context to a workflow for routingdsconfig create-workflow --set base-dn:cn=OracleContext,o=example --set enabled:true --set workflow-element:eusContext --workflow-name exampleContext_workflow -n //Add the new workflow to the appropriate network groupdsconfig set-network-group-prop --group-name network-group --add workflow:exampleContext_workflow -n // Create the local database for o=exampledsconfig create-workflow-element --set base-dn:o=example --set enabled:true --type db-local-backend --element-name example -n // Create a workflow element in the call path to the user data to generate on the fly attributes expected by EUS dsconfig create-workflow-element --set enabled:true --set eus-realm:o=example --set next-workflow-element:example --type eus --element-name eusWfe// Add the db to a workflow for routingdsconfig create-workflow --set base-dn:o=example --set enabled:true --set workflow-element:eusWfe --workflow-name example_workflow -n //Add the new workflow to the appropriate network groupdsconfig set-network-group-prop --group-name network-group --add workflow:example_workflow -n  // Add the appropriate acis for EUSdsconfig set-access-control-handler-prop \           --add global-aci:'(target="ldap:///o=example")(targetattr="authpassword")(version 3.0; acl "EUS reads authpassword"; allow (read,search,compare) userdn="ldap:///??sub?(&(objectclass=orclservice)(objectclass=orcldbserver))";)' dsconfig set-access-control-handler-prop \       --add global-aci:'(target="ldap:///o=example")(targetattr="orclaccountstatusevent")(version 3.0; acl "EUS writes orclaccountstatusenabled"; allow (write) userdn="ldap:///??sub?(&(objectclass=orclservice)(objectclass=orcldbserver))";)' Last but not least you must adapt the content of the ${OUD}/config/EUS/eusData.ldif  file with your suffix value then inport it into OUD.

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• What the best way to wire up Entity Framework database context (model) to ViewModel in MVVM WPF?

  - by hal9k2

  As in the question above: What the best way to wire up Entity Framework database model (context) to viewModel in MVVM (WPF)? I am learning MVVM pattern in WPF, alot of examples shows how to implement model to viewModel, but models in that examples are just simple classes, I want to use MVVM together with entity framework model (base first approach). Whats the best way to wire model to viewModel. Thanks for answers. //ctor of ViewModel public ViewModel() { db = new PackageShipmentDBEntities(); // Entity Framework generated class ListaZBazy = new ObservableCollection<Pack>(db.Packs.Where(w => w.IsSent == false)); } This is my usual ctor of ViewModel, think there is a better way, I was reading about repository pattern, not sure if I can adapt this to WPF MVVM

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• Using EUSM to manage EUS mappings in OUD

  - by Sylvain Duloutre

  EUSM is a command line tool that can be used to manage the EUS settings starting with the 11.1 release of Oracle. In the 11.1 release the tool is not yet documented in the Oracle EUS documentation, but this is planned for a coming release. The same commands used by EUSM can be performed from the Database Console GUI or from Grid Control*. For more details, search for the document ID 1085065.1 on OTN. The examples below don't include all the EUSM options, only the options that are used by EUS. EUSM is user friendly and intuitive. Typing eusm help <option> lists the parameters to be used for any of the available options. Here are the options related to connectivity with OUD : ldap_host="gnb.fr.oracle.com" - name of the OUD server. ldap_port=1389 - nonSSL (SASL) port used for OUD connections.  ldap_user_dn="cn=directory manager" - OUD administrator nameldap_user_password="welcome1" - OUD administrator password Find below common commands: To List Enterprise roles in OUD eusm listEnterpriseRoles domain_name=<Domain> realm_dn=<realm> ldap_host=<hostname> ldap_port=<port> ldap_user_dn=<oud administrator> ldap_user_password=<oud admin password> To List Mappings eusm listMappings domain_name=<Domain> realm_dn=<realm> ldap_host=<hostname> ldap_port=<port> ldap_user_dn=<oud admin> ldap_user_password=<oud admin password> To List Enterprise Role Info eusm listEnterpriseRoleInfo enterprise_role=<rdn of enterprise role> domain_name=<Domain> realm_dn=<realm> ldap_host=<hostname> ldap_port=<port> ldap_user_dn="<oud admin>" ldap_user_password=<oud admin password> To Create Enterprise Role eusm createRole enterprise_role=<rdn of the enterprise role> domain_name=<Domain> realm_dn=<realm> ldap_host=<hostname> ldap_port=<port> ldap_user_dn="<oud admin>" ldap_user_password=<oud admin password> To Create User-Schema Mapping eusm createMapping database_name=<SID of target database> realm_dn="<realm>" map_type=<ENTRY/SUBTREE> map_dn="<dn of enterprise user>" schema="<name of the shared schema>" ldap_host=<oud hostname> ldap_port=<port> ldap_user_dn="<oud admin>" ldap_user_password="<oud admin password>" To Create Proxy Permission eusm createProxyPerm proxy_permission=<Name of the proxypermission> domain_name=<Domain> realm_dn="<realm>" ldap_host=<hostname> ldap_port=<port> ldap_user_dn="<oud admin>" ldap_user_password=<oud admin password> To Grant Proxy permission to Proxy group eusm grantProxyPerm proxy_permission=<Name of the proxy permission> domain_name=<Domain> realm_dn="<realm>" ldap_host=<hostname> ldap_port=<port> ldap_user_dn="<oud admin>" ldap_user_password=<password> group_dn="<dn of the enterprise group>" To Map proxy permission to proxy user in DB eusm addTargetUser proxy_permission=<Name of the proxy permission> domain_name=<Domain> realm_dn="<realm>" ldap_host=<hostname> ldap_port=<port> ldap_user_dn="<oud admin>" ldap_user_password=<oud admin password> database_name=<SID of the target database> target_user=<target database user> dbuser=<Database user with DBA privileges> dbuser_password=<database user password> dbconnect_string=<database_host>:<port>:<DBSID> Enterprise role to Global role mapping eusm addGlobalRole enterprise_role=<rdn of the enterprise role> domain_name=<Domain> realm_dn="<realm>" database_name=<SID of the target database> global_role=<name of the global role defined in the target database> dbuser=<database user> dbuser_password=<database user password> dbconnect_string=<database_host>:<port>:<DBSID> ldap_host=<oid_hostname> ldap_port=<port> ldap_user_dn="<oud admin>" ldap_user_password=<oud admin password>

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• Dynamic Bind9 + DHCP

  - by AcidRod75

  i have been working on setup a server for my internal network, so far i have a working isc-dhcp-server that can upgrade a chrooted BIND9 (on the same machine), i need to add some static entries on the DNS, so users can resolve the websites that resides in our DMZ. What i had tryed all ready was to modify the /etc/bind/named.conf.local with this info: // // Do any local configuration here // // Consider adding the 1918 zones here, if they are not used in your // organization //include "/etc/bind/zones.rfc1918"; key DHCP_UPDATER { algorithm HMAC-MD5.SIG-ALG.REG.INT; secret "MySuperSecretHash"; (this is not the real value BTW) }; zone "quality.internal" IN { type master; file "/var/lib/bind/quality.internal.db"; allow-update { key DHCP_UPDATER; }; }; zone "0.10.10.in-addr.arpa" { type master; file "/var/lib/bind/rev.10.10.0.in-addr.arpa"; allow-update { key DHCP_UPDATER; }; }; logging { channel query.log { file "/var/log/named/query.log"; severity debug 3; }; category queries { query.log; }; }; --- EOF ---- then i added this 2 entries: zone "ourserver.internal" IN { type master; file "/var/lib/bind/ourserver.internal.db"; }; zone "0.16.172.in-addr.arpa" { type master; file "/var/lib/bind/rev.172.16.0.in-addr.arpa"; }; ---- EOF ---- So.. i created the files ourserver.internal.db and rev.172.16.0.in-addr.arpa placed them BOTH in /var/lib/bind/ and changed the permisions so the bind user can access them, restated the service... when i do a NSLOOKUP www.ourserver.internal i get: Server: 127.0.0.1 Address: 127.0.0.1#53 ** server can't find www.ourserver.internal: NXDOMAIN BUT when i do a reverse lookup.... Server: 127.0.0.1 Address: 127.0.0.1#53 5.0.16.172.in-addr.arpa name = www.ourserver.internal I do not understand what's wrong. Some help with this will save me from installing a new DNS server at the DMZ JUST to host internal site names- TY in advance BTW: the server i'm using has Ubuntu Server 11.10 fully patched.

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• The performance implications of IEnumerable vs. IQueryable

  It all started innocently enough. I was implementing a "Older Posts/Newer Posts" feature for my new web site and was writing code like this:IEnumerable<Post> FilterByCategory(IEnumerable<Post> posts, string category) {  if( !string.IsNullOrEmpty(category) ) { return posts.Where(p => p.Category.Contains(category)); }}...  var posts = FilterByCategory(db.Posts, category);  int count = posts.Count();... The "db" was an EF object context object, but it could just as...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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• The performance implications of IEnumerable vs. IQueryable

  It all started innocently enough. I was implementing a "Older Posts/Newer Posts" feature for my new web site and was writing code like this:IEnumerable<Post> FilterByCategory(IEnumerable<Post> posts, string category) {  if( !string.IsNullOrEmpty(category) ) { return posts.Where(p => p.Category.Contains(category)); }}...  var posts = FilterByCategory(db.Posts, category);  int count = posts.Count();... The "db" was an EF object context object, but it could just as...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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• Map, Set use cases in a general web app

  - by user2541902

  I am currently working on my own Java web app (to be shown in interview to get a Java job). So I've not worked on Java in professional environment, so no guidance. I have database, entity classes, JPA relationships. Use cases are like, user has albums, album has pics, user has locations, location has co-ordinates etc. I used List (ArrayList) everywhere. I can do anything with List and DB, get some entry, find etc. For example, I will keep the list of users in List, then use queries to get some entry (why would I keep them in Map with id/email as key?). I know very well the working and features, implementing classes of Map, Set. I can use them for solving some algorithm, processing some data etc. In interviews, I get asked have you worked with these, where have you used them etc. So, Please tell me cases where they should be used (DB or any popular real use case).

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• SS7(M3UA, SCCP, TCAP, MAP) Stack

  - by Ammar Hameed

  I'm building an open source SMSC from scratch; it's almost finished, The SRI and the forwardSM operations are working, but I still have few things to do for the receiving part. I've built the SS7 stack already, but I'm using DB for saving the TCAP transactions IDs to be updated later to get/generate responses. My approach is this: I created memory table (heap table), saved the TCAP TID in the database, then compared the received TCAP TID with the TIDs saved in the database and then decide whether to end the TCAP session or continue. What is the best way to implement it? I'm thinking of doubly linked list that holds the TCAP TID. Am I going towards the right direction, or should I use another technique other than database or D-linked list? Should I leave it as it is, and let the database do the job for saving the TIDs? Please note that I'm using SCTP implementation available on Linux (lsctp) as a transport protocol, the language I'm using is C and the DB is MYSQL.

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• Is there other ways to do insert/update/delete on a remote oracle database?

  - by gunbuster363

  I asked a question recently concerning the speed of execution of insert/update/delete using JDBC driver in a remote machine, but the problem cannot be solved easily. I would like to ask, is there any other way to execute the insert/update/delete to the oracle? The current situation is this: the DB is on a seperate machine than the java program used to update the DB. I looked up the internet and found people suggesting using pure sql or pl/sql to do the update, is that possible? And do we need to operate the sql or pl/sql in a local machine? Because I have no knowledge about pl/sql, so I am not sure if we can create some kind of script and call it on a remote machine. Let say the situation is like this: the input data is on machine A, and the original java program are also on machine A, but the oracle is on machine B. is there any other approach other than JDBC?

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• Does my approach for building a real time monitoring system make sense? [closed]

  - by sameer

  I am developing an application that will display a dashboard that will display data from different SQL databases. This needs to happen in almost real time, our refresh time is about 5 minutes. My approach so far is: Develop a Windows service to accumulate the data from various SQL Server instances. Persist those details into a SQL DB, from which the dashboard will display them on the web page. Trigger fetching of data from the Windows service will every x minutes. The details of the SQL Server instances will be stored in the SQL DB which the Windows service will be referring. Does my approach make sense?

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• Using static in PHP

  - by nischayn22

  I have a few functions in PHP that read data from functions in a class readUsername(int userId){ $reader = getReader(); return $reader->getname(userId); } readUserAddress(){ $reader = getReader(); return $reader->getaddress(userId); } All these make a call to getReader() { require_once("Reader.php"); static $reader = new Reader(); return $reader; } An overview of Reader class Reader{ getname(int id) { //if in-memory cache exists for this id return that //else get from db and cache it } getaddress(int id) { $this->getname(int id); //get address from name here } /*Other stuff*/ } Why is class Reader needed The Reader class does some in-memory caching of user details. So, I need only one object of class Reader and it will cache the user details instead of making multiple db calls. I am using static so that it the object gets created only once. Is this the right approach or should I do something else?

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• Oracle Magazine, January/February 2005

  Oracle Magazine January/February 2005 features articles on better business intelligence, Oracle Forms, Oracle HTML DB, XQuery, tablespace management, Oracle ADF, and much more.

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• Who created that user?

  - by AaronBertrand

  Twitter has provided some great fodder for blog content lately. And twice this week, I've found an excuse to take advantage of the default trace. Tonight @meltondba asked: I'm trying to find who created a user act in a DB It is true, SQL Server doesn't really keep track of who created objects, such as user accounts in a database. You can get some of this information from the default trace, though, since it tracks EventClass 109 (Audit Add DB User). If you run this code: USE [master] ; GO CREATE LOGIN...(read more)

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• What does private cloud Daas or DBaaS really mean ?

  - by llaszews

  Just had meeting with Fortune 1000 company regarding their private DBaaS or DaaS offering. Interesting to see what DBaaS really means to them: 1. Automated Database provisioning - Being able to 'one button' provision databases and database objects. This includings creating the database instance, creating database objects, network configuration and security provisioning. It is estimated that just being able to provision a new DB table in automated fashion will reduce time required to create a new DB table from 60 hours down to 8 hours. 2. Virtualization and blades - DBaaS infrastructure is all based upon VMs and blades. 3. Consolidation of database vendors - Moving from over ten database vendors down to three.

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• MySQLwith mutiple threads and processes

  - by Abhan

  I'm developing a telecom messaging platform in C, and I'm going to need multiple processes to be working with MySQL DB. How can I make two processes read/write to/from a Mysql DB and, if/when one of them goes down, get the other to seamlessly take over the work until the dead process gets back to work? I was thinking/googling some options and am stuck in place where I don't know which one to choose. What I think so far is that table lock is not the best option to go for, as it will stall the other process until the table is unlocked. The other option is to use row-level locks or manual locks, but I can't find the best way to do it.

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• Separating logic and data in browser game

  - by Tesserex

  I've been thinking this over for days and I'm still not sure what to do. I'm trying to refactor a combat system in PHP (...sorry.) Here's what exists so far: There are two (so far) types of entities that can participate in combat. Let's just call them players and NPCs. Their data is already written pretty well. When involved in combat, these entities are wrapped with another object in the DB called a Combatant, which gives them information about the particular fight. They can be involved in multiple combats at once. I'm trying to write the logic engine for combat by having combatants injected into it. I want to be able to mock everything for testing. In order to separate logic and data, I want to have two interfaces / base classes, one being ICombatantData and the other ICombatantLogic. The two implementers of data will be one for the real objects stored in the database, and the other for my mock objects. I'm now running into uncertainties with designing the logic side of things. I can have one implementer for each of players and NPCs, but then I have an issue. A combatant needs to be able to return the entity that it wraps. Should this getter method be part of logic or data? I feel strongly that it should be in data, because the logic part is used for executing combat, and won't be available if someone is just looking up information about an upcoming fight. But the data classes only separate mock from DB, not player from NPC. If I try having two child classes of the DB data implementer, one for each entity type, then how do I architect that while keeping my mocks in the loop? Do I need some third interface like IEntityProvider that I inject into the data classes? Also with some of the ideas I've been considering, I feel like I'll have to put checks in place to make sure you don't mismatch things, like making the logic for an NPC accidentally wrap the data for a player. Does that make any sense? Is that a situation that would even be possible if the architecture is correct, or would the right design prohibit that completely so I don't need to check for it? If someone could help me just layout a class diagram or something for this it would help me a lot. Thanks. edit Also useful to note, the mock data class doesn't really need the Entity, since I'll just be specifying all the parameters like combat stats directly instead. So maybe that will affect the correct design.

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• Saving all hits to a web app

  - by bevanb

  Are there standard approaches to persisting data for every hit that a web app receives? This would be for analytics purposes (as a better alternative to log mining down the road). Seems like Redis would be a must. Is it advisable to also use a different DB server for that table, or would Redis be enough to mitigate the impact on the main DB? Also, how common is this practice? Seems like a no brainer for businesses who want to better understand their users, but I haven't read much about it.

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• Data Source Security Part 4

  - by Steve Felts

  So far, I have covered Client Identity and Oracle Proxy Session features, with WLS or database credentials.  This article will cover one more feature, Identify-based pooling.  Then, there is one more topic to cover - how these options play with transactions.Identity-based Connection Pooling An identity based pool creates a heterogeneous pool of connections.  This allows applications to use a JDBC connection with a specific DBMS credential by pooling physical connections with different DBMS credentials.  The DBMS credential is based on either the WebLogic user mapped to a database user or the database user directly, based on the “use database credentials” setting as described earlier. Using this feature enabled with “use database credentials” enabled seems to be what is proposed in the JDBC standard, basically a heterogeneous pool with users specified by getConnection(user, password). The allocation of connections is more complex if Enable Identity Based Connection Pooling attribute is enabled on the data source.  When an application requests a database connection, the WebLogic Server instance selects an existing physical connection or creates a new physical connection with requested DBMS identity. The following section provides information on how heterogeneous connections are created:1. At connection pool initialization, the physical JDBC connections based on the configured or default “initial capacity” are created with the configured default DBMS credential of the data source.2. An application tries to get a connection from a data source.3a. If “use database credentials” is not enabled, the user specified in getConnection is mapped to a DBMS credential, as described earlier.  If the credential map doesn’t have a matching user, the default DBMS credential is used from the datasource descriptor.3b. If “use database credentials” is enabled, the user and password specified in getConnection are used directly.4. The connection pool is searched for a connection with a matching DBMS credential.5. If a match is found, the connection is reserved and returned to the application.6. If no match is found, a connection is created or reused based on the maximum capacity of the pool: - If the maximum capacity has not been reached, a new connection is created with the DBMS credential, reserved, and returned to the application.- If the pool has reached maximum capacity, based on the least recently used (LRU) algorithm, a physical connection is selected from the pool and destroyed. A new connection is created with the DBMS credential, reserved, and returned to the application. It should be clear that finding a matching connection is more expensive than a homogeneous pool.  Destroying a connection and getting a new one is very expensive.  If you can use a normal homogeneous pool or one of the light-weight options (client identity or an Oracle proxy connection), those should be used instead of identity based pooling. Regardless of how physical connections are created, each physical connection in the pool has its own DBMS credential information maintained by the pool. Once a physical connection is reserved by the pool, it does not change its DBMS credential even if the current thread changes its WebLogic user credential and continues to use the same connection. To configure this feature, select Enable Identity Based Connection Pooling.  See http://docs.oracle.com/cd/E24329_01/apirefs.1211/e24401/taskhelp/jdbc/jdbc_datasources/EnableIdentityBasedConnectionPooling.html  "Enable identity-based connection pooling for a JDBC data source" in Oracle WebLogic Server Administration Console Help. You must make the following changes to use Logging Last Resource (LLR) transaction optimization with Identity-based Pooling to get around the problem that multiple users will be accessing the associated transaction table.- You must configure a custom schema for LLR using a fully qualified LLR table name. All LLR connections will then use the named schema rather than the default schema when accessing the LLR transaction table.  - Use database specific administration tools to grant permission to access the named LLR table to all users that could access this table via a global transaction. By default, the LLR table is created during boot by the user configured for the connection in the data source. In most cases, the database will only allow access to this user and not allow access to mapped users. Connections within Transactions Now that we have covered the behavior of all of these various options, it’s time to discuss the exception to all of the rules.  When you get a connection within a transaction, it is associated with the transaction context on a particular WLS instance. When getting a connection with a data source configured with non-XA LLR or 1PC (using the JTS driver) with global transactions, the first connection obtained within the transaction is returned on subsequent connection requests regardless of the values of username/password specified and independent of the associated proxy user session, if any. The connection must be shared among all users of the connection when using LLR or 1PC. For XA data sources, the first connection obtained within the global transaction is returned on subsequent connection requests within the application server, regardless of the values of username/password specified and independent of the associated proxy user session, if any.  The connection must be shared among all users of the connection within a global transaction within the application server/JVM.

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• Hybrid Columnar Compression

  - by user12620172

  You heard me in the past talk about the HCC feature for Oracle databases. Hybrid Columnar Compression is a fantastic, built-in, free feature of Oracle 11Gr2. One used to need an Exadata to make use of it. However, last October, Oracle opened it up and now allows it to work on ANY Oracle DB server running 11Gr2, as long as the storage behind it is a ZFSSA for DNFS, or an Axiom for FC. If you're not sure why this is so cool or what HCC can do for your Oracle database, please check out this presentation. In it, Art will explain HCC, show you what it does, and give you a great idea why it's such a game-changer for those holding lots of historical DB data. Did I mention it's free? Click here: http://hcc.zanghosting.com/hcc-demo-swf.html

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• MySQL with mutiple threads and processes

  - by Abhan

  I'm developing a telecom messaging platform in C, and I'm going to need multiple processes to be working with MySQL DB. How can I make two processes read/write to/from a Mysql DB and, if/when one of them goes down, get the other to seamlessly take over the work until the dead process gets back to work? I was thinking/googling some options and am stuck in place where I don't know which one to choose. What I think so far is that table lock is not the best option to go for, as it will stall the other process until the table is unlocked. The other option is to use row-level locks or manual locks, but I can't find the best way to do it.

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• Display large amount of data to client through pagination

  - by ebram tharwat

  I have a web application in which i need to show a big number of data or records for clients. Now i 'll use pagination but i was wondering should I: Load all the data once then pagination, sorting and sarching 'll be easy..But it 'll takes big time(using local DB it takes up to 9 sec.) Or each time i show new page(from the pagination) i make a new request to server and then new request to DB to get the next records..But then what if the client click on Prev button, i 'll make a new request to get data that I had previously..Should i cach data that are loaded before and how if that's good technique? So load all data once or make a new request every time i need data that maybe have been loaded before. I'm using ASP.NET MVC SPA with durandaljs and knockoutjs

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• how to serialize function depending on what instance of object calls it, if same instance call in a thread then do serialize else not

  - by LondonDreams

  I have a function which fetches and updates some record from db and I am trying to make sure each if the function is called by same instance of object(same Or different thread) then function should behave synchronized else its a call from different object instance function need not to be synchronized. I have tried it use a lock per client. That is, instead of synchronizing the method directly using explicit locking through lock objects using Map. function is like :- getAndUpdateMyHitCount(myObjId){ //go to db and get unique record by myObjId //fetch value , increment , save update } And this function may get call is same thread by different Or same object instance But as fetching and matching from Map is slow , Is there other optimized way to do this ? Found similar at this Question but dont feel that is optimized

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• PHP - Data Access Layer

  - by scarpacci

  I am currently reviewing a code base and noticed that a majority of the calls (along with DB connections) are just buried inside the PHP scripts. I would have assumed that like other languages they would have developed some sort of data access layer (Like I would do in .Net or Java) for all of the communication to the DB (or implemented MVC, etc). Is this still a common pattern in PHP or is there alternative methodologies/patterns for this technology? I am just trying to understand why the subs would have developed it this way. Any insight/info on how experienced developers design an approach data access in PHP would be very much appreciated.

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