CDC Guide for Linux, UNIX, and Windows

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RAC Considerations

PowerExchange Express CDC for Oracle can capture changes from online and archived redo log files in an Oracle RAC environment.

The PowerExchange Express CDC capture process and PowerExchange Logger for Linux, UNIX, and Windows can run on a RAC member instance or on a server outside of the RAC. In both cases, PowerExchange must have read access to the Oracle online and archived redo logs. For greater resiliency, run the Express CDC capture process and PowerExchange Logger on a server outside of the RAC. With this configuration, if the RAC member node to which PowerExchange is connected fails, Express CDC continues running and tries to connect again. Oracle directs the connection request to another active RAC member that is referenced by an entry in the an Oracle tnsnames.ora file.

To configure PowerExchange for CDC in a RAC, you must define the RAC statement with the MEMBERS parameter in the PowerExchange Express CDC for Oracle configuration file. For the MEMBERS value, enter the maximum number of redo log threads that PowerExchange Express CDC can track for member instances in the RAC, including open and closed threads.

If you do not use ASM and you run the PowerExchange Express CDC capture process and PowerExchange Logger on a server outside of the RAC, you might also need to define the DIRSUB statement. Define the DIRSUB statement if the server where PowerExchange Express capture process runs uses a mount point to the directory with the online and archived redo logs that is different from the mount point that the RAC Oracle instance to which PowerExchange connects uses.

If you use the FAILOVER feature of Oracle, you can define a single entry In the tnsnames.ora file that covers multiple RAC member instances. Informatica recommends that you use the FAILOVER feature to prevent PowerExchange Express CDC for Oracle from failing if a RAC member node stops running. The following sample entry in the tnsnames.ora file has the FAILOVER option enabled and covers two RAC nodes:

ORA1A=
  (DESCRIPTION=
    (FAILOVER=ON)
    (ADDRESS_LIST=
      (ADDRESS=(PROTOCOL=TCP)(HOST=node1.informatica.com)(PORT=1521))
      (ADDRESS=(PROTOCOL=TCP)(HOST=node2.informatica.com)(PORT=1521))
    )
    (CONNECT_DATA=
      (SERVICE_NAME=ORA1A.informatica.com)
    )
  )

If you use ASM, use the following equivalent entry in the tnsnames.ora file:

ASMAny=
  (DESCRIPTION=
    (FAILOVER=ON)
    (ADDRESS_LIST=
      (ADDRESS=(PROTOCOL=TCP)(HOST=node1.informatica.com)(PORT = 1521))
      (ADDRESS=(PROTOCOL=TCP)(HOST=node2.informatica.com)(PORT = 1521))
    )
    (CONNECT_DATA=
      (SERVICE_NAME=+ASM)
    )
  )

SERVICE_NAME must specify a net service name of +ASM.

Also, PowerExchange Express CDC assumes that, for all of the open and closed threads, each is associated with a RAC node. If the number of open and closed threads does not match the Oracle CLUSTER_DATABASE_INSTANCES parameter value, Express CDC issues the following error message:

PWX-36127 ORAD: Enabled thread count does not match instance count. Enabled threads = <number_of_threads> : Cluster Instances = <number_of_instances>.

If you receive this error, disable the redundant threads by using the following SQL statement:

ALTER DATABASE DISABLE THREAD number_of_redundant_threads

Express CDC Considerations

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Table of Contents

CDC Guide for Linux, UNIX, and Windows

CDC Guide for Linux, UNIX, and Windows

RAC Considerations

RAC Considerations