Database Hang on 12c with 'Cursor: Pin S wait on X', 'Row Cache Lock' and 'Library Cache Load Lock'
(Doc ID 2127483.1)
Last updated on JULY 22, 2021
Applies to:Oracle Database - Enterprise Edition - Version 22.214.171.124 to 126.96.36.199 [Release 12.1]
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Express Cloud Service - Version N/A and later
Gen 1 Exadata Cloud at Customer (Oracle Exadata Database Cloud Machine) - Version N/A and later
Oracle Database Cloud Exadata Service - Version N/A and later
Information in this document applies to any platform.
Database hangs periodically with many sessions being blocked by each other, deadlocks can be seen as well, with different waits such as 'cursor: pin S wait on X', 'row cache lock' and 'library cache load lock'.
'Row cache lock' can be on different dictionary cache areas. In this case, they were on dc_objects and dc_histogram_defs.
Looking at the blocker processes in system state dumps we can see the function kkecIsCPUTimeReliable in their call stack.
PARALLEL_DEGREE_POLICY must be set to ADAPTIVE to run into this bug.
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