Weblogic Interview Questions &FAQ's -2

Weblogic Application Server FAQ's - 2

How many WebLogic Servers can I have on a multi-cpu machine?

There are many possible configurations and each has its own advantages and disadvantages. BEA WebLogic Server has no built-in limit for the number of server instances that can reside in a cluster. Large, multi-processor servers such as Sun Microsystems, Inc. Sun Enterprise 10000, therefore, can host very large clusters or multiple clusters.

In most cases, WebLogic Server clusters scale best when deployed with one WebLogic Server instance for every two CPUs. However, as with all capacity planning, you should test the actual deployment with your target web applications to determine the optimal number and distribution of server instances.

How can I set deployment order for applications?

WebLogic Server allows you to select the load order for applications. WebLogic Server deploys server-level resources (first JDBC and then JMS) before deploying applications. Applications are deployed in this order: connectors, then EJBs, then Web Applications. If the application is an EAR, the individual components are loaded in the order in which they are declared in the application.xml deployment descriptor.

How is security handled in the WebLogic J2EE Connector Architecture?

Due to the fact that the current configuration and packaging requirements for resource adapters in WebLogic Server require the hand-editing of the weblogic-ra.xml file, any new passwords specified in the security-principal-map entries are done in clear-text. BEA understands the importance of protecting security passwords. Hence, we provide a Converter Tool that allows for the encryption of all passwords present in the weblogic-ra.xml file. The Converter Tool is shipped in the standard weblogic.jar file.

Why am I getting an "ORA-01000: maximum open cursors exceeded" error, even though I closed all ResultSet, Statement, and Connection objects?

This is an Oracle issue. According to Oracle's documentation, dynamic cursors can remain open from run to run in a session and are not closeable when a procedure closes. To work around this issue, you can increase the number of open cursors allowed in the database or you can reset the connection pool (close and reopen database connections in the connection pool).
To reset the connection pool, you can untarget and retarget the connection pool using the Administration Console. You can also use the reset() method through the JMX API or the RESET_POOL command on the WebLogic Server command line interface.

Can I enable requests to a JDBC connection pool for a database connection to wait until a connection is available?

No, there's no way to allow a request to wait for a pool connection, and from the system point of view there should not be. Each requests that waits for a connection ties up one of the fixed number of execute threads in the server, which could otherwise be running another server task. Too many waiting requests could tie up all of the execute threads and freeze the server.

How do I use multibyte character sets with WebLogic jDriver for Informix?

Currently, multibyte character sets are not supported for the WebLogic jDriver for Informix driver.

Why do I get an exception when trying to find a connection factory?

The exception is usually something like java.io.InvalidClassException or java.lang.NoClassDefFoundError.
Make sure weblogic.jar is in the CLASSPATH of the client. Also make sure you have the correct Java run-time jar files included (i.e., you might need rt.jar).

What can I do when I get java.lang.OutOfMemoryError because producers are faster than consumers?

Quotas can be used to help this situation. Your sender will then receive ResourceAllocationExceptions and the server will stay up. WLS 6.X does not support paging of messages out of memory.
As of WLS 6.1 SP02 or later, you can use the Message Paging feature, which can free up valuable virtual memory during peak message load periods by swapping out messages from virtual memory to persistent storage when message loads reach a specified threshold.

Which XML parser comes with WebLogic Server ?

We bundle a parser, based on Apache's Xerces 1.3.1 parser, in WebLogic Server. In addition, we include a WebLogic proprietary high-performance non-validating parser that you can use for small to medium sized XML documents. The WebLogic XML Registry allows you to configure the parser you want to use for specific document types.

How do I turn the auto-deployment feature off?

The auto-deployment feature checks the applications folder every three seconds to determine whether there are any new applications or any changes to existing applications and then dynamically deploys these changes.

The auto-deployment feature is enabled for servers that run in development mode. To disable auto-deployment feature, use one of the following methods to place servers in production mode:

* In the Administration Console, click the name of the domain in the left pane, then select the Production Mode checkbox in the right pane.
* At the command line, include the following argument when starting the domain's Administration Server:

-Dweblogic.ProductionModeEnabled=true

Production mode is set for all WebLogic Server instances in a given domain.

Can I set the deployment order for application modules? For standalone modules?

The Load Order attribute controls the deployment order of standalone modules and applications relative to other modules and applications of the same type. For example, standalone EJBs with smaller Load Order values are deployed before those with higher values.

Modules that are deployed as part of an Enterprise Application (EAR file or directory) are deployed in the order in which they are specified in the application.xml deployment descriptor.

What is the difference between the WL_HOME/config/examples/applications folder and the WL_HOME/config/examples/stage folder?

The applications folder is intended for applications that are not yet ready for a production environment. WebLogic Server dynamically deploys the contents of the applications folder. The stage folder (or a folder that you create for the same purpose) is for storing copies of deployment files that are ready for deployment in a production environment (deployments that use the stage or external_stage deployment modes).

How can I set deployment order for applications?

WebLogic Server allows you to select the load order for applications. WebLogic Server deploys server-level resources (first JDBC and then JMS) before deploying applications. Applications are deployed in this order: connectors, then EJBs, then Web Applications. If the application is an EAR, the individual components are loaded in the order in which they are declared in the application.xml deployment descriptor.

Can I refresh static components of a deployed application without having to redeploy the entire application?

Yes. You can use weblogic.Deployer to specify a component and target a server, using the following syntax:
java weblogic.Deployer -adminurl http://admin:7001 -name appname -targets server1,server2 -deploy jsps/*.jsp

When should I use the -nostage option?

Set the staging mode to -nostage (using weblogic.Deployer or the Administration Console) if you don't want to copy deployment files but want to deploy an application from its present location. All target servers must be able to access the same set of deployment files.

When should I use the external_stage option?

Set -external_stage using weblogic.Deployer if you want to stage the application yourself, and prefer to copy it to its target by your own means.