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Lock Pages in Memory

It is generally recommended that 'lock pages in memory' be enabled for your SQL Servers to prevent the OS paging out SQL Server memory.

how do you do this?

Well, the answer is straight forward...If you have SQL Server Enterprise Edition:

You allocate the service account running SQL Server the 'Lock Pages In Memory' permission.

How Can I Tell if 'Lock Pages in Memory is Enabled?'

Note

I am using Windows 2003 R2 and SQL Server 2008 SP1 for this demo but I have also done this on Windows 2008 R2 and it works just the same way. It is a 64 bit environment.

If you are running SQL Server with the Local System account, I know most of you are not, but for those of you that are, SQL Server will automatically 'lock pages in memory'. Bob Ward has a blog post on this here: (http://blogs.msdn.com/b/psssql/archive/2007/10/18/do-i-have-to-assign-the-lock-privilege-for-local-system.aspx)

If you are using the local system or a domain account with appropriate permissions you will see an entry similar to the following at the start of the SQL Server log:

LockPagesInMemoryIsEnabled

Therefore if you are running SQL Server using a domain account and the domain account does not have the necessary permissions to lock pages in memory then you will not have this message in the log:

LockPagesInMemoryIsNotEnabled

If you do not have 'Lock Pages In Memory' enabled and you would like too enable it then follow these steps:

Logon to the SQL Server in question

Click <Start><Run> and enter 'secpol.msc' in the run box.

In the 'Local Security Policy' window that opens expand <Local Policies> and <User Rights Assignment> in the left hand pane.

LocalSecurityPolicyWindow

In the right hand pain scroll down to the 'lock pages in memory' policy. Right Click, select <Properties> <Add User or Group> and add the domain account that is running the SQL Service and click <OK>

LockPagesInMemory

That's it, you need to restart the SQL Server service for the change to take effect, the next time that SQL Server starts up you should see

LockPagesInMemoryIsEnabled

in the SQL Server log.

Standard Edition

Up until SQL Server 2005 SP3 Cumulative Update Package 4 and SQL Server 2008 SP1 Cumulative Update Package 2 'Lock Pages in Memory' was not supported in SQL Server Standard Edition.

You may find this link helpful

http://support.microsoft.com/kb/970070

as you need to request the CUs from Microsoft. They will then send you a link to download the CU.

These two CUs add the 'lock pages in memory' option for SQL Server Standard edition.

Note you you have to enable trace flag 845 to for standard edition to be able to 'lock pages in memory.'

Virtualisation, SQL Server and Lock Pages

Are you running SQL Server in Virtual Land, well here is something else to to consider care of Mr Denny:

http://itknowledgeexchange.techtarget.com/sql-server/vmware-and-sql-and-lock-pages-in-memory/


Comments

Posted by kennethigiri on 3 July 2010

I think this will be very useful. We have had this paging out error for quite a while.

However, are there any possible negetive effects on the OS? Can the OS be denied memory for other processes if SQL Server locks memory assuming one does not have sufficient RAM?

Posted by Gethyn Ellis on 5 July 2010

Hi

Glad you like the post. If you are worried about starving the OS of memory then you could set the max memory setting. For example say you have a server with 6GB of RAM and the server runs one instance, then you could set the max memory setting to say 4GB that way you always have 2GB reserved for the OS.

Posted by ALZDBA on 6 July 2010

Thanks for bringing this back into focus.

Keep in mind you should set MAX SERVER MEMORY (KB) for the sqlserver instance. (because it will nolonger free up RAM if needed by other processes)

I always recommend reading these articles to prep lock pages in memory usage:

How to reduce paging of buffer pool memory in the 64-bit version of SQL Server(support.microsoft.com/.../918483)

Lock Pages in Memory ... do you really need it? (blogs.technet.com/.../lock-pages-in-memory-do-you-really-need-it.aspx)

and SQLOS's memory manager and SQL Server's Buffer Pool ( blogs.msdn.com/.../371063.aspx )

Posted by Gethyn Ellis on 6 July 2010

That's a nice set of links, thanks for the comment and including the links.

Posted by J.Wilson on 4 October 2010

....i did not i knew it!

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