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SAP with Microsoft SQL Server 2005: Best Practices for High Availability, Maximum Performance, and Scalability69

SQL Server 2005, Enterprise Edition (64-bit)

SQL Server 2005 Enterprise Edition (64-bit) supports both the IA64 and x64 computing platforms and makes no distinction between these platforms concerning their limitations. SQL Server 2005 (64-bit) provides an increased linear address space, without requiring the use of an additional layer such as AWE.

In terms of memory handling, the 32-bit virtual memory constraints can inhibit the use of SQL Server 2005 and slow performance in memory-intensive applications. This includes SAP products that store and process large amounts of data in memory. For example, with SQL Server 2005 (64-bit), complex queries can be assigned higher quotas on buffers based on real memory.

The following is a comparison of 64-bit memory addressability on quotas:

32-bit computing. For a complex query, a quota in SQL Server 2005 can be assigned no more than 25 percent of the data buffers for sort, group, or hash operations. Assuming a virtual address space of 3 GB is configured for SQL Server 2005, roughly 700 MB could be assigned for this query at best. When more space is needed, parts of the intermediate data of the query are pushed to disk in tempdb. Using AWE would not change this behavior.

64-bit computing. If the same complex query were run on SQL Server 2005 (64-bit) on a server with 64 GB of memory, the query can be assigned up to 16 GB of memory to perform joins, sorts, and grouping, leaving only a very small number of queries that need tempdb. Most queries can be performed fully in memory by using the data buffers available to SQL Server 2005 (64-bit), greatly improving performance.

In addition, having the capability to address more than 64 GB of memory directly provides opportunities that were previously unavailable because of the drawbacks of the 32-bit platform. Doubling or quadrupling memory can dramatically reduce the I/O rate. This improves the response time by a factor of 2 to 4 and lowers investment costs for I/O hardware. In addition, SQL Server 2005 (64-bit) can be expanded in workload areas that could not be touched with 32-bit platforms.

Microsoft x64 computing platform

The SQL Server 2005 (64-bit) x64 computing platform is a Microsoft architecture that extends the x86 instruction set to 64 bits. SQL Server 2005 uses Windows Server 2003 x64 Edition and requires drivers and software that are specifically compiled for the x64 instruction set. Windows Server 2003 (64-bit) supports both the AMD Opteron and Intel processors with Extended Memory Technology (EM64T).

The Microsoft x64 platform offers support both for 32-bit and 64-bit computing. Existing 32-bit software can be used without being recompiled. The x64 computing platform can act as an x86 processor when an x64 system is booted into a 32-bit operating system.

Note that the SQL Server 2005 (64-bit) x64 platform does not run 64-bit IA64 versions of the Windows Server operating system or 64-bit IA64 drivers that are compiled for Itanium. The 64-bit IA64 platform is not compatible with SQL Server 2005 (64-bit). Different sets of executables are required.

Microsoft Corporation © 2005

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