Thursday, 14 July 2011

Significant virtual memory paging was detected on the host OS windows

During my experimentation with ADDM with Oracle10g on Windows 2008 x64 I found frequent warning at the top of the report, such as:
Significant virtual memory paging was detected on the host operating system.

RECOMMENDATION 1: Host Configuration, 100% benefit (8567 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.
I knew that this message is likely a bogus one, considering that Windows OS handles virtual memory a bit different than other operating systems. If you launch Task Manager you can easily observe Page Faults rapidly increasing during warm up phase of the Oracle instance (for example after fresh startup):

Note:395957.1 ADDM Reports "Significant Virtual Memory Paging Was Detected On The Host Operating System"
================SOLUTION FROM ORACLE =====================

Applies to:
Oracle Server - Enterprise Edition - Version: 10.2.0.2
z*OBSOLETE: Microsoft Windows Server 2003
z*OBSOLETE: Microsoft Windows Vista x64 (64-bit)
Microsoft Windows (32-bit)
z*OBSOLETE: Microsoft Windows XP
Microsoft Windows Itanium (64-bit)
z*OBSOLETE: Microsoft Windows Server 2003 R2 (64-bit AMD64 and Intel EM64T)
Microsoft Windows x64 (64-bit)
z*OBSOLETE: Microsoft Windows Vista (32-bit)

Symptoms

On a Windows system (32 or 64 bit) Automatic Database Diagnostic Monitor (ADDM) reports:

=========================
FINDING 1: 100% impact (858 seconds)
Significant virtual memory paging was detected on the host operating system.

RECOMMENDATION 1: Host Configuration, 100% benefit (858 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.
=========================

Cause

The Windows operating system handles virtual memory differently from other operating systems.

NOTE: This condition is Oracle version independent as it is a function of the Windows Operating System

Solution
High virtual memory use is not a problem on Windows platforms unless you are experiencing database performance issues.
Therefore, ignore the recommendation/action by ADDM unless you are experiencing database performance issues


=======================================================================

My recommendation is that ADDM advice on Windows platform should be cross checked with OS trying to find out if real memory paging is going on. If you found that for example Oracle process Peak Memory Usage is (was) close to the amount of physical memory, it's very likely that ADDM warning is not a bogus one and that real memory paging is going on, that need to be addressed.


3 comments:

  1. http://www.dbaportal.eu/?q=node/97 similar article :)

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  2. Copy & Paste

    http://www.dbaportal.eu/?q=node/97

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