If PowerExchange receives null restart tokens for all sources in a CDC session, it uses the default restart points.
For DB2 for i5/OS sources, the default restart points vary by extraction mode, as follows:
For batch extraction mode and continuous extraction mode, the default restart point is the oldest condense file that is recorded in the CDCT file.
For real-time extraction mode, the default restart point is the oldest journal receiver that is still attached on the journal receiver chain.
PowerExchange uses the default restart point only if all sources in a CDC session have null restart tokens. If some sources have non-null restart tokens, PWXPC assigns the oldest restart point from those tokens to any sources for which no restart tokens are specified.
For example, a new CDC session contains the sources A, B, and C. The restart token file contains restart tokens for sources A and B. The restart point for source A is older than that for source B. Source C does not have existing or supplied restart tokens. Because some sources in the CDC session have explicit restart points, PWXPC does not assign null restart tokens to source C. Instead, PWXPC assigns the restart point for source A to source C because this restart point is the oldest one supplied.