Bug 12633340 – RISK SESSION SPIKE – LIBRARY CACHE LOCK AND LIBRARY CACHE: MUTEX X

Bug 12633340 – RISK SESSION SPIKE – LIBRARY CACHE LOCK AND LIBRARY CACHE: MUTEX X
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@ Readme Instructions:
@ The patch must be enabled by setting event 12633340 to level 1. It can
@ be set in the init.ora or via alter system. If set in the init.ora,
@ please note that all events must be specified on consecutive lines. If
@ set via alter system, it will take effect only for new sessions
@ that connect after that point in time.
@ .
@ event=”12633340 trace name context forever, level 1″
@ .
@ This patch amends an earlier fix that was made in bug 6769075. Due to
@ that fix, cursor reloads may take longer in a highly concurrent environment
@ if that cursor was invalidated due to a DDL operation. With this patch,
@ the reload issue should be fixed and it should resolve the related mutex
@ contention. Note that this patch is not meant to eliminate all mutex
@ contention in general. It should however eliminate or minimize mutex
@ and library cache lock waits associated with the “build lock” for
@ the cursor after DDL has occurred.

Bug 16870682 – ESSC: LIBRARY CACHE LOCK 60%, MUTEX X 20%, CONCURRENT DDL, DML, Q ON PT
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@ I would say all three changes helped but is mostly the event 12633340, level
@ 4 which seems to have the greatest share