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SAP with Microsoft SQL Server 2005: Best Practices for High Availability, Maximum Performance, and Scalability38

awe enabled

The awe enabled option is used with a larger data buffer to maximize the virtual address space for high-end database servers using the 32-bit platform (x86). Address Windowing Extensions (AWE) cannot be used with any of the 64-bit platforms. AWE administrated memory only can be used for data pages. Caches and structures such as statement or procedure cache, lock structures, and buffer headers remain in the virtual address space and do not use memory accessed over AWE functionality.

To use the awe enabled option, the /PAE option must be set in the boot.ini file of the Windows operating system.

The user context used to start SQL Server requires permission to lock pages in memory.

For SAP, the 3-GB virtual address space is typically used, although some customers only require a 2-GB virtual address space. The 3 GB of memory is enabled by adding the /3gb option in the boot line in the boot.ini file.

In some cases, using up to 16 GB of real memory in 32-bit high-end dedicated database servers that are configured to use AWE with a 14-GB (maximum) cache can achieve a positive customer experience for some SAP workloads. However, using more than 16 GB of memory on a 32-bit SQL Server 2005 platform under a SAP workload is not recommended. If more than 16 GB of memory is required, it is recommended that the client move to a 64-bit computing platform. For more information, see 64-Bit Computing Configurations in this paper.

For SAP to use up to 16 GB of real memory, set the max server memory option to a fixed value of 14 to 15 GB maximum and assign the set working set size option to 0. During startup, SQL Server allocates the AWE portion of the memory immediately.

Note that the memory usage of the SQL Server process is not indicated correctly by the Windows Server 2003 Task Manager. The footprint of the SQL Server process shows a very low number of bytes that does not reflect reality.

However, the commit charge under the Performance tab of the Windows Server 2003 Task Manager indicates when a large amount of memory was allocated. The allocation of AWE memory can extend the startup time of SQL Server to about a minute.

lightweight pooling

In general, the lightweight pooling option is not recommended because it results in only minor performance improvements. This option is typically used for benchmark workloads that are extremely uniform.

Note that in the past, activating lightweight pooling (set to 1) was recommended for running a server based on the Unisys ES7000 architecture.

Microsoft Corporation © 2005

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