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Weblogic Application Server FAQs

181.Explain about WebLogic Production Redeployment?

    1. Production redeployment:
      1. Allows two versions of a single Web application or module to run simultaneously
      2. Requires you to include unique version information either:
        • Within the application’s META-INF/MANIFEST.MF file
        • As part of the deployment process
    2. When a new version is redeployed, WLS automatically:
      • Routes existing clients to the prior (retired) version
      • Routes new clients to the new version
      • Undeploys the prior version when all existing clients finish their work or their conversations time out

182.What are the Requirements and Restrictions for Production Redeployment in WLS?

    1. Production redeployment is supported for:
      • Stand-alone Web Application (WAR) modules and Enterprise Applications (EARs) whose client accesses the application via a Web application (HTTP)
      • Enterprise Applications that are accessed by inbound JMS messages from a global JMS destination, or from inbound JCA requests
      • All types of Web Services, including conversational and reliable Web Services
    2. Production redeployment is not supported for:
      • Stand-alone EJB or Resource Archive (RAR) modules
      • Applications that use JTS drivers
      • Applications that obtain JDBC data sources via the DriverManager API instead of using the JNDI lookup
      • Applications that include the EJB 1.1 container-managed persistence (CMP) EJBs
    3. A deployed application must specify a version number.
    4. WLS can host a maximum of two different versions of an application at one time.
    5. When you are redeploying a new version of an application, the following features cannot change:    
      • Deployment targets
      • Security model
      • Persistent store settings

183.Redeploying Versus Distributing an applications in WLS?

    1. Distributing is an alternative to deploying an application.
      • Distributing an application prepares it for deployment by copying its files to all target servers and validating the files.
      • You can start a distributed application in Administration mode. Access to the application is then restricted to a configured Administration channel.
    2. Distributing a new version of the application makes it available for testing before being released for general consumption.
    3. Redeploying a new version of an application places the application immediately into use and makes it available to new client requests.

184.How will you Distributing a New Application Version in WLS?

    1. Use the weblogic.Deployer –distribute command.
    2. After the application is distributed, start the application in Administration mode.
    3. Test the application.
    4. When ready, start the application (without using –adminmode).
    5. Optionally set a retirement timeout for the older version of the application.

185.How will you Create MANIFEST.mf file for Production Redeployment?

    1. Create MANIFEST.mf with the following contents:
      Name: java/util/
      Specification-Title: Java Utility Classes
      Specification-Version: 1.2
      Specification-Vendor: Sun Microsystems, Inc.
      Implementation-Title: java.util
      Implementation-Version: build57
      Implementation-Vendor: Sun Microsystems, Inc.
    2. Then add an entry for WLS versioning:

                Weblogic-Application-Version: Version1.0Beta
186.What is a cluster Definition?

    1. A cluster is a group of Oracle WebLogic Server instances that work in coordination.
    2. Clustering provides:
      • High availability
      • Load balancing
      • Scalability

187.What Is a Cluster?
A cluster:

    1. Is a logical group of Oracle WebLogic Servers within a domain
    2. Supports features to
      provide high
      availability for:
      • Whole servers
      • Web applications/services
      • EJB applications
      • JMS
    3. Is transparent to a client

188.What are the Benefits of Clustering?

    1. There are two main benefits of clustering together Oracle WebLogic Servers:
      1. Scalability
      2. High availability
    2. Scalability is the ability to provide more capacity for an application, in this case, by adding additional servers without having to make major architectural changes.
    3. High availability ensures that when a server (in a cluster) fails, there are other servers to take over the work, so that the client is not affected.

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189.What are the Key Capabilities of clustering?
The key capabilities of a WebLogic cluster are:

    1. Application failover
      • When an object in an application that is performing a task becomes unavailable, another object takes over and finishes
        the job.
    2. Site failover
      • When all the services and applications in a single site fail, they can switch to a separate site and continue processing.
    3. Server migration
      • When a server fails, pinned services can be migrated to another server in a cluster.
    4. Load balancing
      • Tasks and communications are evenly distributed across multiple servers.

190.Explain about Cluster Architecture?

    1. Applications are generally broken into multiple tiers, each representing its distinct functionality:
      1. Web tier
      2. Presentation tier
      3. Business or object tier
    2. WebLogic provides clustering support for all three tiers.
    3. Other services, such as JMS and JDBC, can take advantage of clusters but load-balancing and failover is a little different.