Large volume columns and SQL

Db2 logs changes to LOB objects differently than changes to non-LOB objects.

The log records of a delete action that affects a LOB column do not include the LOB column data. Similarly, the log records of an update to a LOB column do not contain the 'before image' of the LOB column.

Related topic

Considerations-for-output-files-and-SQL

Despite these differences, BMC AMI Log Master can generate UNDO SQL to undo the effect of a delete action on a LOB column. BMC AMI Log Master can generate UNDO SQL to undo an update action on a LOB column (depending on the presence of image copies or other log records).

This restriction does not apply to

  • Inline LOB columns when the LOB is contained entirely in the inline section, and you use Data Capture Changes (DCC)
  • XML columns

The XML table space or LOB table space that corresponds to a large volume column (or a partition of the column) can be logged or not logged at the discretion of database administration personnel. If a large volume table space is not logged, BMC AMI Log Master cannot generate SQL for changes to the corresponding large volume column. In this situation, BMC AMI Log Master generates SQL statements for changes to all other columns, but does not generate changes for either the unlogged column or the corresponding table space.

 

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