ADDM Reports Significant Virtual Memory Paging on Linux When None is Occurring [ID 1322964.1]

In this Document

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Applies to:

Oracle Database - Enterprise Edition - Version 10.2.0.5 to 11.2.0.2 [Release 10.2 to 11.2]
Linux x86-64
Linux x86
Linux Itanium

Symptoms

After upgrading the database to 10.2.0.5, the ADDM report on Linux operation system may include findings on "Significant virtual memory paging":

FINDING 1: 100% impact (32719 seconds)
--------------------------------------
Significant virtual memory paging was detected on the host operating system.

RECOMMENDATION 1: Host Configuration, 100% benefit (32719 seconds)
ACTION: Host operating system was experiencing significant paging but
no particular root cause could be detected. Investigate processes that
do not belong to this instance running on the host that are
consuming significant amount of virtual memory. Also consider adding more
physical memory to the host.

There is no evidence at OS level of any problem with virtual memory paging. To verify that you are not really observing a memory problem, look at an operating system memory tool, such as vmstat:

oracle$ vmstat 5 5
procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
 r  b   swpd   free   buff  cache      si   so    bi    bo   in   cs us sy id wa st
 1  0 670056 1184580  35772 12809336    0    0    26    40    1    5  3 27 68  1  0
 0  0 670028 1183624  35788 12810980    0    0     7    22 1298 2534  3  1 90  6  0
 1  0 670016 1171840  35804 12813436    0    0     2    34 1621 2691  5  1 77 16  0
 1  0 669996 1175536  35816 12817064    0    0     6    19 1424 2957  9  2 77 12  0
 0  0 669968 1183408  35840 12820460    0    0     8    28 1430 2850 14  3 73 10  0

Note: Under swap, si and so show a value of 0.
As above, if there are no abnormal figures and you are still seeing this warning, you might me hitting this problem

Cause

This issue can be seen from 10.2.0.5 to 11.2.0.2

The problem is caused by wrong values in V$OSSTAT as explained in:
Bug 10148787 ADDM REPORTS VIRTUAL MEMORY PAGING AFTER APPLYING 10.2.0.5
and unpublished Bug 11712010 VIRTUAL MEMORY PAGING ON 11.2.0.2 DATABASES.

Solution

In 11.2, the fix is included in the Patch 10220118 documented in Document 10220118.8 NEED TO ALERT WHEN SYSTEM IS CLOSE TO PAGING. This patch includes an enhancement adding a warning to be printed to the alert log (and DBRM trace) if excessive swapping is observed on the system.

In 10.2.0.5 , please apply patch 12347332.

References

BUG:10148787 - ADDM REPORTS VIRTUAL MEMORY PAGING AFTER APPLYING 10.2.0.5

BUG:12347332 - TRACKING BUG TO FIX ADDM INCORRECTLY REPORTING PAGING ON 10.2.0.5