Change Data Capture places constraints on both database Reorgs and Load Replace operations. Two items in particular are important the Db2 Compression Dictionary and Db2 Logging:
Db2 compression dictionary
Before the Connect CDC (SQData) Db2/z capture agent can read the Db2 recovery log records, Db2 must decompress the log records of any table that is stored in a compressed table space. Db2 uses the current compression dictionary for decompression. If the CDC process is run asynchronously, for some reason gets behind or is configured to recapture older logs, the proper Compression Dictionary may be unavailable if a database Reorg or Load Replace has occurred.
In Precisely's experience, customers have already specified the KEEPDICTIONARY=YES parameter when usingusing the Db2 REORG or LOAD utility. This parameter should be confirmed prior to implementation of the Db2/z Change Data Capture.
- Altering a table space to change its compression setting
- Using DSN1COPY to copy compressed table spaces from one subsystem to another, including from data sharing to non-data-sharing environments.
- Running the REORG or LOAD utility on the table space.
Db2 logging
The Db2 Load/Replace operation clearly impacts the content of Db2 Tables that are a source for Change Data Capture. In addition to the other prerequisites for Db2/z Capture, the Load/Replace operation requires RESUME with SHRLEVEL CHANGE to log change data for Connect CDC (SQData) to capture.