Get Information About: Cache invalidation in Oracle Applications

Cache invalidation in Oracle Applications

With the extended usage of Self Service Web Applications(SSWA) in Oracle Applications, the mechanism of cache invalidation assumes significant importance. In the process of supporting Oracle Application i am sure most of you would have already come across the cache invalidation mechanism and problems associated with it in Oracle Applications.

What do you mean by cache Invalidation?

The main purpose of the web cache is to cache frequently used data and reduce application response time for the end user. However in order to maintain the relevance of the cached data it is important that the old is flushed out or invalidated and new data is cached again. This process is referred to as cache invalidation. All the web server which support web cache have different mechanisms to deal with the invalidation process. These may be time based date based etc.Also invalidation maybe either automatic that is triggered by the application /Server itself or it may be manual like from the console or a simple deletion from the backend.

Cache Invalidation In Oracle Applications

The core web server of Oracle Applications is the apache based Oracle Application Server. The Oracle application Server Web Cache has the ability to cache both static and dynamic data.

The different methods of Invalidation supported by the Oracle Application Server Web Cache are

Manual Invalidation through Web Server Console

Manual invalidation through a telnet to the web server.

Invalidation using PL/SQL,this is available via the wxvutil.sql scriptthe which can be obtained from http://otn.oracle.com/software/products/ias/web_cache/files/api_plsql.zip

Invalidation from a JSP using the jesi:invalidation tag

Based on the circumstances encountered Oracle Applications also uses these mechanisms to perform cache invalidation to render the most relevant information when using self service web applications.

Oracle Applications implements a Cache Framework to effectively handle the caching mechanisms in E-Business Suite. This framework primarily includes

Cache Manager: The cache manager is responsible for interacting between the business APIs and the cache components. The business APis request data from the cache via this manager.

Cache Components: The actual data is stored in the form of cache components. The data is distributed in various cache components based of the attributes.

Cache Class Loader: Each of the cache components are associated with a cache calss loader. when the data is requested by the business APIs via the cache manager to the cache component, if the object is present it is given back and in case of a miss (also referred as a cache miss) the cache class loader is responsible for fetching the data from the database and loading it into the cache component.

A common case of improper of cache invalidation is when you add a self service responsibility to a user and the user is not able to see that responsibility immediately. A work around is that you manually clear the cache or bounce your web server after which the change is reflected (as it does a force invalidation of your cache).However if you have applied your latest patches and roll ups you would not see this problem.

The Oracle Application cache Framework supports the following features

Preloading: Preloading allows certain objects to be preloaded in the cache component along with the startup of the JVM. This increases performance by eliminating the need to lod the objects via the class loader.

Distribution: In case of multiple JVMs in use the caching framework ensures that cache changes and invalidations are propogated in all the caches.

Dadatabse Invalidation. the caching framework in applications also provides for an invalidation request to be originated from the database level. This means the database cahnges to the cached objects are sent as invalidation requests to the cache. To enable this feature you must however make sure that the Workflow Java Deferred Agent Listener is started in your instance.

Event Support: Also supported by the applications cache framework is the support for events. This ensures that there is synchronization between inter dependent data in the cache. For this purpose event handlers are registered within the cache components.

You can run diagnostic test on your cache by going to the

http://<hostname>:<port>/OA_HTML/jtflogin.jsp

Another mechanism adopted by the web cache along with invalidation is Expiration. Expiration happens when the objects in the web cache are marked as invalid after a certain period of time. While invalidation is used for randomly changing objects the expiration method is adopted for objects which do not change so frequently.

Posted by Sam at 03:11 AM | Permalink | Comments (1) | TrackBacks (0)

April 07, 2007

Installing Oracle Enterprise Linux

Installing Oracle Enterprise Linux

During the last years Oracle Open World when Oracle released the Oracle Enterprise Linux it took many of us by surprised. Though i had felt oracle would sooner or later venture into the OS market i did not expect it to happen so soon.

I had put up a post on Oracle Enterprise Linux when the OOW was in progress. Since then i was waiting get my hands on this product. Finally i did find a chance to install and evaluate Oracle Enterprise Linux.In the current post i am talking abut my experience with this new Linux offering from Oracle.

You can download a copy of the Oracle Enterprise Linux from

http://edelivery.oracle.com/linux

After you make the selection for the type of Linux you will get the following parts

Enterprise Linux 4 update 4 for x86 (CD 1 of 8)

Enterprise Linux 4 update 4 for x86 (CD 2 of 8)

Enterprise Linux 4 update 4 for x86 (CD 3 of 8)

Enterprise Linux 4 update 4 for x86 (CD 4 of 8)

Enterprise Linux 4 update 4 for x86 Source (CD 5 of 8)

Enterprise Linux 4 update 4 for x86 Source (CD 6 of 8)

Enterprise Linux 4 update 4 for x86 Source (CD 7 of 8)

Enterprise Linux 4 update 4 for x86 Source (CD 8 of 8)

If you do not want the source code and just need to install Linux you can do with downloading the first four parts only.These parts are in a zip format iso images so you may want to burn them on your CD or DVDs before you can proceed with the installation.

To start the installation you must set your server to boot up with the CD rom and insert the frist CD.

The first screen after you get after your server boots up with the Oracle Linux CD 1 will give you options either to do a text based installation or a graphical UI installation.

I selected the GUI installation, the next screen you get is the welcome message from Oracle Enterprise Linux installation.

Now select the language in which you want to do your installation in, remember this is not your OS default language.

Next make a selection for the type of keyboard you have on your server.

Next select the type of instillation you wish to have, most likely you will have to choose server if you are installation it on a server and plan to use it for Oracle Applications.

Now select the method you wish to use to create your disk partitions. You can either do it manually using fdisk or use a GUI based tool like disk druid.

I used disk druid and made the following partitions.

/

/usr

swap

/boot

/u01

/u02

Now select the file system where you want to install your boot loader. You can choose not install a boot loader also but in that case you would need to create a boot disk for your server to start up.

Next specify the hostname and domain name details of your server, also you can specify your DNS settings and you gateway information here.

Next is the firewall configuration settings, be sure to disable your firewall and SELinux if you plan to install Oracle Applications. The runInstaller will not be able to ping your database with the firewall on.At a later stage if you wish you can choose to enable your firewall.

Next you select the default language for your enterprise linux server.

Next select the time zone for your server.

Now select the OS packages you wish to install, again if you planning for Oracle applications it is important that you install all the development packages.

The installer will now prompt you to start the installation.

As a first step the installer first created and formats the partitions that you defiened using Disk Druid earlier.

The installation then starts which should take an approximate of 20-30 minutes based your server hardware configuration.

After the installation is complete the installer will ask you to reboot your server after removing any bootable disk from the CDRom drives.

After the server boots up you must provide some post installation information, like time and date as well as your sound card test and display before you can start using your server.

As a part of your post installation step you are also asked to create a non system users to perform general system administration.

After you complete you post installation you can log in to your Oracle enterprise Linux as root or any other newly created user.

The Oracle Enterprise Linux now loads up with a nice looking finilar interface