ADDM Reports bug:Significant virtual memory paging was detected on the host operating system，addmpaging

ADDM Reports bug:Significant virtual memory paging was detected on the host operating system，addmpaging

查看ADDM（數據庫版本為ORACLE 10.2.0.5.0）報告時，發現其中有個結論非常不靠譜：Significant virtual memory paging was detected on the host operating system，具體內容如下所示：

FINDING 2: 100% impact (3930 seconds)

-------------------------------------

Significant virtual memory paging was detected on the host operating system.

   RECOMMENDATION 1: Host Configuration, 100% benefit (3930 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.

使用nmon監控並沒有發現消耗大量虛擬內存（virtual memory），搜索了一下，發現這個是一個bug導致。ORACLE 10g， ORACLE 11都有出現這個問題.

官方ADDM Reports Significant Virtual Memory Paging on Linux When None is Occurring (文檔 ID 1322964.1)介紹如下所示

 

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. 

ORACLE 10.2.0.5 可以通過下載補丁補丁程序12347332: TRACKING BUG TO FIX ADDM INCORRECTLY REPORTING PAGING ON 10.2.0.5解決這個Bug