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Row completion processing and your jobs

The following table summarizes key concepts of row completion processing and the impact it can have on your jobs.

Category

Information

Key concepts

  • DB2 log records for insert and delete actions contain a complete image of the table row. DB2 log records for update actions might not contain a complete image. Unless the table is defined with Data Capture Changes (DCC), the update log records might contain only part of the table row (enough to include all of the changed data).

  • Log Master needs complete row images to produce complete output. If a table is not defined with DCC, the product must perform row completion processing to obtain the complete image of each update action.

  • Log Master uses the following sources to complete log records:

    • The current table space

    • Image copies

    • Other DB2 log records (for example, insert or delete actions of the same table row)

  • Log Master uses record IDs (RIDs) to perform row completion processing.

Impact

  • To produce complete output, row completion processing requires additional time and resources.

  • Jobs that perform row completion processing usually read more log than they would without row completion; sometimes much more log. These jobs can also mount and read image copies.

  • Events that change the locations of rows, such as database reorganization or load actions, can assign different rows to existing record ID (RID) values and affect how Log Master performs row completion processing.

    (PTF BQU1717 applied) When the events are modified out of SYSIBM.SYSCOPY, BMC recommends performing REPOS UPDATE INCLUDE SYSCOPY to store the SYSCOPY records in the Repository so that completion can be performed and optimized, and compression processing can correctly use valid compression dictionaries to scan the DB2 log across these events. If the records are not in the Repository but are needed after a modify utility is used, you can use REPOS UPDATE INCLDUE SYSCOPY with the START option to retrieve the SYSCOPY records from the log.

  • To reduce row completion processing:

    • Define your tables with DCC

    • Create image copies more frequently

This section contains the following topics:

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