In the last entry posted to this blog , I described the mechanisms (including PUNC bits and commit log sequence numbers, aka CLSNs) used by Db2 for z/OS for lock avoidance purposes (lock avoidance here refers to a capability whereby Db2 can, in many cases, verify the committed state of a data value without having to get an S-lock – i.e., a read lock – on the page or row in which the value is located). As lock and unlock requests consume CPU cycles, lock avoidance is a CPU efficiency booster for Db2 …read more


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