SQL Server Performance

How can you tell if /3GB is working

Discussion in 'Performance Tuning for Hardware Configurations' started by phcahill, Jul 7, 2005.

  1. phcahill New Member

    Windows 2000 Advanced Server and Sql 2000 EE. Dell Poweredge 8450 with 4GB ram.

    I understand about the 2GB+2GB partitioning but how can you tell (an independant test) that /3GB has had any effect.

    Using /PAE windows task manager displays 4GB ram and the memory slider in SQL goes up to 4GB.

    Using /3GB windows task manager displays 2GB ram and the memory slider in SQL goes up to 2GB.

    Is that what you see? I'm not suprised at task manager but why does the slider in SQL EE not go up to 3GB with /3GB switch.

    I had tried sp_configure to set to 2500MB but the sql server working set/virtual bytes never goes above 2GB. In fact they hover just below 2GB.

    So how can I tell for sure that /3GB has enabled correctly. It is possible to knock up a C++ program to test via api?

    Thanks
    Paul
  2. satya Moderator

    If AWE is not enabled, SQL Server can only see up to 2GB. However, if you enable /3GB in boot.ini, SQL Server can then see up to 3GB. SQL Server will only take advantage of the more than 2GB memory if you use /PAE, /3GB in boot.ini, and enable AWE. Make sure you set Max memory to about 6.5GB, or so. KBAhttp://www.microsoft.com/isapi/gosupport.asp?TARGET=/KB/274750 for your information.

    Satya SKJ
    Moderator
    http://www.SQL-Server-Performance.Com/forum
    This posting is provided “AS IS” with no rights for the sake of knowledge sharing.
  3. gurucb New Member

    What does Virtual bytes Peak for the sql server process indicate?

    If /3GB is enabled it should see more than 2 Gigs atleast in Virtual bytes....
    But usage depends on sQl Server load or max memory setting.

    As a test include only /3GB in boot.ini and check perfmon counters for virtual and virtual bytes peak put server under load.











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