5.4.1 Prerequisite configuration

If you want to use the session failover functionality, a system configuration that uses a load balancer and distributes requests on multiple J2EE servers, is a prerequisite. Moreover, it is necessary to deploy a database for storing HTTP session information that is created on each J2EE server.

The database session failover functionality does not support Oracle Database connections based on Oracle RAC.

The following figure shows the prerequisite configuration for using the database session failover functionality.

Figure 5‒3: Prerequisite configuration for the session failover functionality

• Load balancer

  For using the session failover functionality, use of a load balancer is a prerequisite.

  Reference note

  Distributing a request with a load balancer

  Requests are distributed with a load balancer. This distributes the load, achieving stable operations of the system and improving processing performance.

  The load balancing performed by using a load balancer has the advantage that the load related to the load balancing processing is not applied to the Web server and J2EE server. Methods for the request distribution vary according to the load balancer.

  The following figure shows an example of distributing requests by using a load balancer.

  Figure 5‒4: Example of request distribution by using a load balancer

• The J2EE server or Web server

  For using the session failover functionality, arrange one or more J2EE servers and Web servers in one system. We recommend that you arrange two or more servers in the preparation for a J2EE server failure.

• Database

  When using the database session failover functionality, a database is required as a storage location of session information. The following table describes mapping of the databases, which you can use as a storage destination of session information, JDBC drivers, and resource adapters.

  Table 5‒4: Mapping of databases, JDBC drivers, and resource adapters which you can use

  Database	JDBC driver	Resource adapter#
  HiRDB	HiRDB Type4 JDBC Driver	DBConnector_HiRDB_Type4_CP.rar
  Oracle	Oracle JDBC Thin Driver	DBConnector_Oracle_CP.rar

  # DB Connector is the resource adapter used in the database session failover functionality. For details on the settings required for DB Connector used in the database session failover functionality, see 6.6.4 DB Connector settings.

  For details on the system configuration for using the database session failover functionality, see 3.10.1 Configuration using a database (database session failover functionality) in the uCosminexus Application Server System Design Guide.

  If the configuration that uses the database session failover functionality satisfies the conditions described here, you need not redesign from the system configuration. You can use the database session failover functionality if you implement the functionality settings and perform parameter tuning.

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