When you use a group definition file, CDC sessions can extract change data more efficiently by targeting a more specific set of condense files.

To use a group definition file with z/OS data sources, you must set the

Condense

option to

Part

in the capture registrations. You cannot use the

Full

condense option.

Also, you must specify the fully qualified data set name for the group definition file in the GROUPDEFS parameter in the CAPTPARM configuration member.

Without a group definition file, PowerExchange Condense processes data for all tables that are registered with the

Condense

option set to

Full

or

Part

. All changes are written to a single set of condense files, not taking into account file-switching. To extract change data from a table with low level of change activity, the extraction process might need to read a lot of data before finding the changes of interest.