Wrong wait events in 11.2 ("cursor: mutex S" instead of "cursor: mutex X") (文档 ID 9591812.8)

Bug 9591812  Wrong wait events in 11.2 ("cursor: mutex S" instead of "cursor: mutex X")

 This note gives a brief overview of bug 9591812. 

 The content was last updated on: 28-JUN-2013

 Click here for details of each of the sections below.

Affects:

Product (Component)	Oracle Server (Rdbms)
Range of versions believed to be affected	Versions >= 11.2 but BELOW 12.1
Versions confirmed as being affected	11.2.0.2 11.2.0.1
Platforms affected	Generic (all / most platforms affected)

 It is believed to be a regression in default behaviour thus:

   Regression introduced in 11.2.0.1

Fixed:

This issue is fixed in

12.1.0.1 (Base Release) 11.2.0.3 (Server Patch Set) 11.2.0.2.2 Database Patch Set Update 11.2.0.2 Bundle Patch 3 for Exadata Database 11.2.0.1 Bundle Patch 8 for Exadata Database 11.2.0.2 Patch 3 on Windows Platforms

Symptoms:	Related To:
Diagnostic Output Problem / Improvement Waits for "cursor: mutex S" Waits for "cursor: mutex X" Waits for "cursor: pin S" Waits for "cursor: pin X"	Performance Monitoring V$SESSION_WAIT

Description

When examining information related to performance,
a wait for a cursor mutex in exclusive mode
('cursor: mutex X') may be incorrectly shown
as a wait in share mode ('cursor: mutex S').
Also a "cursor: pin X" wait may be shown as "cursor: pin S".

eg:
The processstate of a waiting process shows something like:
Current Wait Stack:
0: waiting for 'cursor: pin S'
idn=0x10439dee, value=0xffffffffffffffff, where=0x100000000

but the mutex information in the trace shows a GET_LONG_EXCL request:
KGX Atomic Operation Log c0000005255cc710
Mutex c000000528a43b30(-1, -1) idn 10439dee oper GET_LONG_EXCL
Cursor Pin uid 764 efd 0 whr 1 slp 27284

Rediscovery Notes:
If the call stack or processstate of a session shows that
it is waiting for a cursor mutex in exclusive mode
GET_LONG_EXCL but V$SESSION_WAIT and other performance-related
view show that it is waiting for the mutex in share mode
('cursor: mutex S' or 'cursor: pin S').

Workaround
Be cautious when interpreting S mode mutex / pin waits.

Please note: The above is a summary description only. Actual symptoms can vary. Matching to any symptoms here does not confirm that you are encountering this problem. For questions about this bug please consult Oracle Support.

References

Bug:9591812 (This link will only work for PUBLISHED bugs)
Note:245840.1 Information on the sections in this article

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