Logging Mode for sbspaces

About this task

Enterprise Replication uses the default log mode that the sbspace was created with for spooling row data.

Create sbspaces with a default logging mode of ON or OFF according to the types of transactions Enterprise Replication replicates:
  • LOGGING=ON

    Create sbspaces with LOGGING set to ON to support these situations:

    • Replicated systems with high-availability clusters

      Enterprise Replication must use logging sbspaces for transactions involved in high-availability clusters.

    • Small transactions

      Enterprise Replication uses logging sbspaces for transactions that are less than a page size (2K or 4K) of replicated data.

    For logging sbspaces, performance might be enhanced because logging mode enables asynchronous IO. However, a logging sbspace consumes additional logical-log space.

  • LOGGING=OFF

    Create sbspaces with LOGGING set to OFF to support replication of large transactions (greater than a page size of replicated data).

    It is recommended that you mirror non-logging sbspaces. For more information, see the chapter on managing disk space in the HCL OneDB™ Administrator's Guide and the HCL OneDB Administrator's Reference.

    For non-logging sbspaces, performance is enhanced on the database server when Enterprise Replication spools to disk because Enterprise Replication writes less data to disk.

Important: Do not change the Enterprise Replication sbspace default log mode while Enterprise Replication is running. To change the default log mode, follow the procedure below.

You can change the default logging mode of the row data sbspace if you have more than one sbspace specified by the CDR_QDATA_SBSPACE configuration parameter.

To change the default logging mode of a row data sbspace:

Procedure

  1. Shut down the database server.
  2. Remove the sbspace from the CDR_QDATA_SBSPACE configuration parameter value list.
  3. Start the database server in recovery mode.
  4. Wait for all the smart large objects to get deleted from the sbspace. Use the onstat -g smb lod command to check for smart large objects stored in an sbspace.
  5. Change the default logging mode for the sbspace.
  6. Add the sbspace name to the CDR_QDATA_SBSPACE configuration parameter value list.
  7. Shut down and restart the database server using the onmode -ky and oninit commands.