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[数据库]ADDM Reports bug:Significant virtual memory paging was detected on the host operating system


查看ADDM(数据库版本为ORACLE 10.2.0.5.0)报告时,发现其中有个结论非常不靠谱:Significant virtual memory paging was detected on the host operating system,具体内容如下所示:

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.


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使用nmon监控并没有发现消耗大量虚拟内存(virtual memory),搜索了一下,发现这个是一个bug导致。ORACLE 10g, ORACLE 11都有出现这个问题.

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官方ADDM Reports Significant Virtual Memory Paging on Linux When None is Occurring (文档 ID 1322964.1)介绍如下所示

 

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 5procs -----------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 可以通过下载补丁补丁程序12347332: TRACKING BUG TO FIX ADDM INCORRECTLY REPORTING PAGING ON 10.2.0.5解决这个Bug