Oracle KGX mutexes appeared more than 7 years ago. However, mutex waits are still obscure. Oracle Documentation provided only brief description of mutex wait events without any information about wait durations and timeouts.
Look at the following timeline:
- In 2005 mutexes were introduced with Oracle 10.2.0.2 patchset. Documentation states that “cursor: pin S” wait event should rarely be seen.”
- In June 2008, Oracle released Patch 6904068: High CPU usage when there are “cursor: pin S” waits. Patch used “_first_spare_parameter” to tune the waits duration.
Latch, mutex and beyond 