Oracle9iAS TopLink Oracle Application Server Tips by Burleson Consulting

Oracle9iAS TopLink is an important component for Java developers because it provides a mechanism for making Java objects persistent across sessions.  In object-oriented languages such as Java, C# or C++, objects can be instantiated and destroyed according to the needs of the program.

The problem is that OO languages like Java create objects in the RAM heap, and upon termination of the program, all of the programs objects are destroyed.  Oracle9iAS TopLink is a persistence framework that enables object persistence by supplying routines that can be invoked to store Java objects in relational database tables (in any relational database that supports JDBC).  In addition, Oracle9iAS TopLink provides a GUI tool, the Mapping Workbench, that greatly simplifies the task of mapping Java objects and their attributes to database tables.  TopLink also provides powerful features like a query framework, object-level transaction support, relationship mappings, object caching, and much more.  Prior to TopLink, the programmer would have to write custom JDBC code to store and retrieve the Java object?s attributes to/from a relational table. This is extremely time-consuming and error prone plus difficult to change. TopLink is built on top of JDBC but does not require developers to use JDBC (or even SQL!).  Oracle9iAS TopLink supports all J2EE compliant application servers, and can be used to store object data from standard Java objects, as well as entity beans. Please refer to the Oracle9iAS TopLink documentation for more information.

Next, let?s introduce the main topic of this text, the administration and management of Oracle9iAS.

Oracle9iAS Administration

Unlike an Oracle database, which has only a few administrative interfaces (OEM, SQL*Plus), Oracle9iAS has many administrative utilities.   To make matters even more challenging, the Oracle9iAS administrative tools are often tightly coupled, as in the case of the Oracle9iAS web cache administration pages and the Oracle HTTP server administration pages.  Both of these administrative interfaces are separate, yet they are closely intertwined in the Oracle9iAS architecture. 

Oracle9iAS provides two methods for administration, the command-line interface and Oracle Enterprise Manager.  This book will show both methods, and the choice of Oracle9iAS administration methods is largely a personal choice.

We will start with a review of each administrative component and then look at using OEM and the command line interfaces within each component.

Oracle9iAS Administrative Component Overview

As an Oracle9iAS administrator it is your job to become intimate with all of the Oracle9iAS management components.  Of course, your shop may not have some of the optional components such as single sign-on, but it is imperative that you understand the administrative components and how they fit together.  This section will review the general administration tools, web cache administration tools and application layer administration tools.  Let?s take a closer look at each of these sections. 

Oracle9iAS general administration components

Here are the main administrative interfaces for the Oracle9iAS Infrastructure.

• LDAP Server (OID) ? This is the Oracle Internet Directory (OID) component of Oracle9iAS.  The LDAP server is the foundation of the Oracle9iAS automated provisioning methodology, and the Oracle9iAS administrator must manage the LDAP repository (the directory), to maintain user-access privileges

• Single Sign-On (SSO) ? The SSO component provides for centralized management among all of the Oracle9iAS components.  Large shops may have dozens of Oracle9iAS components, and SSO allows for easy password management and access control.

• Metadata Repository (isadb) ? The isadb is an Oracle databases that stores configuration information and metadata. This includes data used by LDAP, OMS and SSO.

• Mod_osso Module ? The mod_osso module is used to provide communication between the SSO-enabled Login Server and the Oracle HTTP Server (OHS) listener. The mod_osso module is controlled by editing the mod_osso.conf file.

Oracle9iAS web administration components

From the top-down, the webserver component (web cache and OHS) is one of the most important components of Oracle9iAS, and one where tuning is the most important.  For details on Oracle9iAS web cache and Oracle HTTP Servers, see Chapter 10.

• Oracle HTTP server (OHS) ? This is the HTTP listener software that intercepts incoming requests and routs them to the appropriate Oracle9iAS component.  Upon completion of the transaction, the OHS send the completed HTML or XML back to the originating IP address.

• Web cache ? This component is associated with am OMS instance and server to provide RAM caching for images (gif?s and jpeg?s), as well as page content.  The Web Cache and the OHS are closely-coupled, and the tuning of the Web Cache is addressed in Chapter 10.

Oracle9iAS application management components

Moving down the Oracle9iAS hierarchy we next see the administrative tools for application development, primarily for Java applications.  The Oracle9iAS administrator must use these interfaces to ensure optimal configuration of their systems.

J2EE Server (OC4J) ? This component allows you to deploy and manage Java-based applications. The Oracle9iAS administrator must configure the J2EE server to ensure proper communications between OC4J and other Oracle9iAS components.

Oracle Process Manager and Notification (OPMN) ? OC4J is started and managed with OPMN.  OPMN is also responsible for monitoring all Oracle9iAS processes and propagating configuration changes across Oracle9iAS clusters.

Distributed Configuration Management (DCM) ? DCM is a handy command-line utility that can used instead of the GUI for starting and stopping Oracle9iAS services.

Now that we see the different administrative components, let?s take a review of how you can use Oracle Enterprise Manager (OEM) or the command line interfaces to manage Oracle9iAS.

Command line interfaces or OEM?

As we have already noted, the Oracle9iAS administrator has two choices for administering Oracle9iAS, the OEM console GUI or the command line interfaces.  Using the OEM console, the GUI will issue the appropriate commands without you having to memorize the syntax.  On the other hand, many experienced Oracle9iAS administrators find that the command-line interface offers a full-range of administration commands. 

Of course, some tasks must be done from the command line interfaces.  For example, you cannot use OEM until the OMS is started, so you must issue the emctl start oms command before you can use OEM.  Internally, it makes no difference if you use OEM or a command-line utility to manage Oracle9iAS.  This is because the OEM Console uses DCM (the dcmctl utility) to make configuration changes and to propagate configuration changes and deployed applications across the cluster.

WARNING: If you use the infrastructure and you manually edit the configuration files, you may introduce corruption into the Oracle9iAS Infrastructure. This is true for both V9.0.2 and V9.0.3. Be sure to shutdown the Enterprise Manager website (emctl stop) before using dcmctl to change configuration. If/when both are used "at the same time" there is a strong possibility that the  infrastructure data may become corrupted and you may have to re-install Oracle9iAS.  The dcmctl -updateConfig command can be used to notify the environment that config files were updated so that the changes are properly picked up.  This requirement will be referenced throughout the book.

Let?s start with a quick tour of OEM for Oracle9iAS and then review the command line interfaces.

This is an excerpt from "Oracle 10g Application Server Administration Handbook" by Don Burleson and John Garmany.