AWE & Lock pages

  • Hi Experts,

    I have read most of the specs on the net and also most of the content related to memory in BOL, but it is still confusing.

    For 64 bit , AWE will not come in to picture. This statement i have read from BOL.

    But recently we started supporting a 64 bit server in which AWE is enabled, Can anyone confirm is it as expected.

    Second Question

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

    When Lock pages in momory in enabled for the account which runs under sql server, then this info should be logged in the server logs--

    To my Knowledge and also read from BOL.

    But when i checked the logs there is no information about lock pages. So can any one confirm lock pages in memory is working perfectly or not.

    Can any one share some light how to check whether this lock pages in memory working fine as expected.

    Regards,

    Sandhya

  • Hi,

    This is the case we are using in our organization:

    - Windows 2003 Server 64Bit

    - SQL Server 2008 64Bit

    - AWE is not enabled

    - RAM : 48 GB

    and around 46 GB is using right now (nothing has been done in 64Bit).

    Sani

  • The AWE Enabled checkbox is still there on a 64-bit version of SQL server, it just doesn't do anything useful; whether it's on or off the server can still access as much RAM as you have installed.

  • Hi,

    Thanks for the reply. I'm clear on the first question.

    Can you assiat in the second question.

    Second Question

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

    When Lock pages in momory in enabled for the account which runs under sql server, then this info should be logged in the server logs--

    To my Knowledge and also read from BOL.

    But when i checked the logs there is no information about lock pages. So can any one confirm lock pages in memory is working perfectly or not.

    Can any one share some light how to check whether this lock pages in memory working fine as expected.

  • Second Question:

    You should have this message in the SQL Server Log:

    Message

    Using locked pages for buffer pool.

    It's after the CPU check.

    Did you restart the server after setting "lock pages in memory" for the sql server service account?

  • The AWE setting is not required for a 64-bit server to access memory above 4GB, but it does have a slight effect.

    Memory acquired through the AWE API is not considered part of the process working set, so it cannot be paged out by the OS. That's why its considered locked in memory, and why the SQL Server account needs the "lock pages in memory" permission to use AWE.

    Enabling AWE on a 64-bit server doesn't make any extra memory available, but it does give a slight performance gain to the OS kernel. Since the AWE-allocated memory is off limits for paging, the virtual memory system effectively has less memory to manage.

    Edit:

    The "slight performance gain" is a valid claim, but the above explanation of how it works is a gross oversimplification. For more detailed info:

    http://blogs.msdn.com/psssql/archive/2009/09/11/fun-with-locked-pages-awe-task-manager-and-the-working-set.aspx

    http://blogs.msdn.com/slavao/archive/2005/04/29/413425.aspx

  • When you check AWE in a 64bit instance, nothing happens. If you lock pages in memory, it makes use of the awe api. Set a max memory setting and you can prevent paging of the buffer cache for a nice performance benefit. Now, other processes can affect the memory usage and make sql trim it's working set, but thats another story.

  • sandhyarao49 (4/28/2010)


    When Lock pages in momory in enabled for the account which runs under sql server, then this info should be logged in the server logs--

    To my Knowledge and also read from BOL.

    But when i checked the logs there is no information about lock pages. So can any one confirm lock pages in memory is working perfectly or not.

    Can any one share some light how to check whether this lock pages in memory working fine as expected.

    Have you checked that the trace flag is being set on startup? -T845

    Without this Standard edition doesn't actually use Locked Pages. The requirement is not that well documented.

    Cheers

    Leo

    Leo
    Nothing in life is ever so complicated that with a little work it can't be made more complicated.

  • Sandhya:

    I recently used this article as reference and works perfect. You should be able to see the message in the sql log if configured correctly. Thanks

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