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Improve poor query compilation performance due to long lock list traversal in DB2 10.1 and later
Beginning with DB2 LUW 10.1 DGTT-referencing DML started to take catalog locks and therefore we have to free them and potentially traverse long lock chain if the DML is a part of a long-running transaction potentially holding millions of locks. This severely affects compile performance and as a result slows down the overall transaction. This situation is explained in CRM 04397,SGC,821 in detail.
In short, in DB2 10.1 we have moved some tablespace information out of the packed descriptor and as a result, we end up making a new call to a newly implemented SYSTABLESPACES cache.Â This call will acquire locks thus turning on the flag in DPS and triggering the necessary free_cat_locks call.Â Â Locking developers investigated the issue and determined that any change to improve performance in this area is too big to be done through a defect.
Please refer to CRM 04397,SGC,821 for more detailed analysis.
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