5.10 Considerations when executing an SQL statement that creates work tables
If data sort processing or deduplication is performed during execution of an SQL statement, a work table might be created in the work table DB area. Data being sorted or data after deduplication is stored temporarily in a work table. Therefore, if you sort a large amount of data or perform deduplication for such data, sufficient performance improvement might not be obtained due to the workload of creating work tables.
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To avoid performance degradation, you must estimate accurately the size of the work table DB area that is needed. If more SQL statements for which work tables are created are executed than initially expected, the application program developer must request that the HADB system designer or system administrator re-estimate the size of the work table DB area.