This Db2 for z/OS News from the Lab blog entry was originally published on 2018-10-26.

By Wei Li and Michael Wendel.

Db2 12 function level 503 (V12R1M503) introduces a new built-in global variable, SYSIBMADM.REPLICATION_OVERRIDE, that provides support needed to replicate system-period temporal tables or tables that contain generated expression columns.

This built-in global variable is not intended for general use. It is intended for use on the apply side of the replication process by products that enable replication of Db2 data. As such, write privileges on the variable are not granted to PUBLIC.

To enable this new capability in your environment, you'll need to take steps similar to the following:

• Activate FL503 or above on the Db2 target subsystem (sometimes called the apply side of a replication process)
• Apply and activate FL503-related maintenance on the replication product (for example, APAR PI99238 for InfoSphere Data Replication 11.4 - Q Replication)
• Rebind the replication application on the Db2 target with APPLCOMPAT V12R1M503 or above

Applications that set the SYSIBMADM.REPLICATION_OVERRIDE global variable must be bound using APPLCOMPAT V12R1M503 or above.

When the override is in effect, insert or update operations can specify a value for row-begin, row-end, transaction-start-ID, or generated expression columns. Normally, Db2 always generates the values for these types of columns. Also, when the override is in effect, historical rows are not written to the associated history tables for update and delete operations on system-period temporal tables. System-period temporal tables normally generate historical rows for update and delete operations.

Overriding normal Db2 behavior for system-period temporal tables and generated expression columns allows applications that replicates Db2 data to specify values that exactly match the source table, ensuring that the replicated Db2 data is accurate.

With the addition of the SYSIBMADM.REPLICATION_OVERRIDE global variable, the SYSPROC.SET_MAINT_MODE_RECORD_NO_TEMPORALHISTORY stored procedure is deprecated at APPLCOMPAT V12R1M503.

Learn more about function level 503.