Thursday, October 4, 2007

Oracle : Support for Very Large Memory (VLM) Configurations

Oracle Database for Windows supports Very Large Memory (VLM) configurations in Windows to access more than the 4 gigabyte (GB) of RAM traditionally available to Windows applications.

The requirements for taking advantage of this support are:

  1. The computer on which Oracle Database is installed must have more than 4 GB of memory.

  2. The operating system must be configured to take advantage of Physical Address Extensions (PAE) by adding the /PAE switch in boot.ini. See Microsoft Knowledge Base article Q268363 for instructions on modifying boot.ini to enable PAE.

  3. It is advisable (though not necessary) to enable 4GT support by adding the /3GB parameter in boot.ini. See Microsoft Knowledge Base article Q171793 for additional requirements and instructions on modifying boot.ini to enable 4GT.

  4. The user account under which Oracle Database runs (typically the LocalSystem account), must have the "Lock memory pages" Windows 2000 and Windows XP privilege.

  5. USE_INDIRECT_DATA_BUFFERS=TRUE must be present in the initialization parameter file for the database instance that will use VLM support. If this parameter is not set, then Oracle Database 10g Release 1 (10.1) behaves in exactly the same way as previous releases.

  6. Initialization parameters DB_BLOCK_BUFFERS and DB_BLOCK_SIZE must be set to values you have chosen for Oracle Database.

  7. Registry parameter AWE_WINDOW_MEMORY must be created and set in the appropriate key for your Oracle home. This parameter is specified in bytes and has a default value of 1 GB. AWE_WINDOW_MEMORY tells Oracle Database how much of its 3 GB address space to reserve for mapping in database buffers.
  8. Once this parameter is set, Oracle Database can be started and will function exactly the same as before except that more database buffers are available to the instance. In addition, disk I/O may be reduced because more Oracle Database data blocks can be cached in the System Global Area (SGA).

  9. If DB_BLOCK_SIZE is large, however, the default AWE_WINDOW_MEMORY value of 1 GB may not be sufficient to start the database.
Reference Note:

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