Advantages of a 64-bit Environment

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Advantages of a 64-bit Environment

SQL Server Technical Article

Writers: Joe Yong, Darshan Singh, Larry Chesnut (Scalability Experts, Inc.)

Technical Reviewer: Mitch Gatchalian, Anish Patel (Microsoft Corporation)

Published: November 2005

Updated: January 2007

Applies To: SQL Server 2005

Summary: Microsoft SQL Server 2005 (64-bit) offers dramatic improvements in memory availability and parallel processing performance when compared to SQL Server software running in a 32-bit environment. This paper describes the capabilities of the 64-bit solution, highlights differences from the 32-bit environment, and discusses some of the applications and usage scenarios that can benefit from running on a SQL Server platform optimized for the 64-bit environment. The paper helps the reader to identify workloads that will benefit from Microsoft SQL Server 2005 (64-bit) and to set appropriate expectations for deployment and performance.


The information contained in this document represents the current view of Microsoft Corporation on the issues discussed as of the date of publication. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information presented after the date of publication.


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 2005 Microsoft Corporation. All rights reserved.

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The names of actual companies and products mentioned herein may be the trademarks of their respective owners.


Executive Summary 1

Introduction 3

Audience 3

Overview: Database Performance and Scalability 3

SQL Server 2005 (64-bit) 5

SQL Server 2005 (64-bit) hardware requirements 6

SQL Server 2005 (64-bit) components 7

Advantages of the 64-bit architecture 8

SQL Server 2005 (32-bit) with AWE 8

AWE: An overview 8

Limitations of AWE 9

AWE does not increase Virtual Address Space 9

Considerations for Choosing SQL Server 2005 (64-bit) 10

Relational database performance factors 11

Analysis Services considerations 13

Integration Services considerations 14

Reporting Services considerations 15

Server consolidation considerations 15

SQL Server 2005 (64-bit) Deployment Considerations 16

Integration 16

Mission-critical safety net 17

Compatibility issues 17

Migration 18

Drivers for 64-bit 18

Summary 19

Conclusion 20

Executive Summary

The first version of the Microsoft® Windows® 64-bit (Itanium) operating system was released in August 2001. Microsoft SQL Server™ (64-bit) was released in April 2002. Since then, the 64-bit computing world on the Windows platform has changed significantly. In true Moore’s law fashion, not only are 64-bit hardware prices on the decline, but performance has seen tremendous improvements. Further accelerating the price decline is the introduction of x64 platforms by both Intel (EM64T) and AMD (AMD64). This event lowered the 64-bit entry price by an order of magnitude, while overall 64-bit platform gains hover around 200%. The latest SQL Server 64-bit TPC-C benchmark results (at the time of writing of this paper) achieved over one million TPC-C transactions/minute at a cost of 5.38 US $ per tpmC1.

To further simplify customer adoption, the latest version of the Microsoft Windows XP and Windows Server™ 2003 operating systems and SQL Server 2005 are available in three binaries—32-bit (x86), x64, and Itanium. Customers considering deploying SQL Server 2005 can decide on the optimal hardware platform for their business applications and overall information technology (IT) infrastructure. Two key factors will motivate the rapid adoption and deployment of SQL Server 2005 (64-bit).

First, there are clear industry dynamics around the longer-term prospects of 64-bit computing that need to be noted. Many industry experts and analysts anticipate that by the end of 2005, virtually all of Intel and AMD’s server processors will be 64-bit enabled, either natively or with 64-bit extensions. This is further supported by a poll in Information Week during Q4, 2004 on 64-bit platform adoption. In this poll, almost a third of the respondents are already running primarily 64-bit servers while 36% will do so within two years. According to another study by major industry analyst The Gartner Group2, 64-bit processors with multiple cores will dominate the markets by the year 2007. Even the latest Itanium chip code named Montecito (at the time this paper is written) is dual-core and hyper-threading capable. It is clear that the industry is gravitating towards the 64-bit platform and doing so at an accelerated pace, at least for server- and workstation-class computers. That said; 64-bit notebook/portable computers have also been available since the start of 2005.

Second, the actual benefits that SQL Server 2005 (64-bit) will bring to customers are compelling. In the areas of supportability, manageability, scalability, performance, inter-operability and business intelligence, SQL Server 2005 provides far richer 64-bit support than its predecessor. All of the features and service components of SQL Server, such as SQL Server Integration Services (SSIS), Analysis Services, Reporting Services, Microsoft Search and Notification Services can run natively on x64 or Itanium-based systems. In addition, all SQL Server 2005 tools will run and are fully supported on both platforms. Therefore, adoption and supportability of applications will no longer be primarily focused on memory-starved systems or systems that have load characteristics suitable for Itanium architecture. For example, SQL Server workloads that exhaust the virtual memory limits imposed by 32-bit servers can now run on x64. Applications requiring supercomputer horsepower (workload suitable for large memory and Itanium’s EPIC architecture) can run on Itanium-based systems and probably even on the soon-to-arrive highly processor-scalable x64 multicore solutions.

This paper describes the performance, operability and manageability enhancements offered by SQL Server 2005 (64-bit). Through an objective comparison of 32-bit and 64-bit environments, this paper addresses the questions “When and why should I move to 64-bit computing with SQL Server 2005?”

This paper also discusses the value drivers for 64-bit adoption including:

  1. Overall reduction in total cost of ownership (TCO) through reduced licensing fees and higher transaction throughput.

  2. Reduced operating costs through server consolidation.

  3. Large scale business intelligence (BI) and online transaction processing (OLTP) scalability without application changes.


Microsoft SQL Server 2005 Standard and Enterprise Editions (64-bit) offer dramatic improvements in memory availability and parallel processing performance when compared to SQL Server software running in a 32-bit environment. This paper describes the capabilities of the 64-bit solution, highlights differences from the 32-bit environment, and discusses some of the applications and usage scenarios that can benefit from running on a SQL Server platform optimized for a 64-bit environment. The paper is intended to help the reader identify potential applications for Microsoft SQL Server 2005 (64-bit) and set appropriate expectations for deployment and performance.

Many customers have been pleasantly surprised with the cost benefits they obtained by migrating to a 64-bit version of SQL Server. For example, a leading healthcare and medical supplier company which ships over 1.7 million critical medical orders annually gained almost 2.5 times the transaction processing capabilities when they switched from 32-bit to 64-bit SQL Server. On top of that, the cost of the new 64-bit server hardware was only 10% higher than the cost of the original 32-bit server (bought just 15 months earlier)3. If you want the most scalable system, you might choose a server with the ability to scale up to 64-way IA64 processors, and 1 terabyte of RAM. If your corporate strategy is to build a server farm of multiple 64-bit servers, you might choose an x64 based system. If you want to run 32-bit applications on your 64-bit server, then you might again choose an x64 system with dual cores.

In the long run, customers may find that the total cost of ownership for SQL Server 2005 (64-bit) is less expensive than SQL Server 2005 (32-bit). One might ask, "How can that be?" For starters, performance on the 64-bit platform can be significantly greater than on a 32-bit equivalent. Additionally, the 64-bit platform provides far greater headroom for growth. This means that the hardware lifecycle is likely to be longer, especially with the release of multicore (currently dual-core) 64-bit CPUs. The 64-bit platform is also very well-suited for supporting multiple OLTP and analytical workloads within the same server thus reducing hardware, license, operations, and infrastructure costs. This means that the same server will meet your requirements for a longer period, while taking up less floor space in your data center and costing less to maintain.

You might incur lower licensing costs by running the 64-bit version. For example, you could choose between a four-way 32-bit server and a two-way 64-bit server. The annual licensing costs of the 64-bit platform would be half that of the 32-bit platform and performance returns will lean heavily toward 64-bit. Would the lower license costs outweigh the more expensive hardware? The answer might very well be "yes." The benefits are significant, especially on the x64 platforms now available from both Intel and AMD. Soon both companies will be delivering to the market place in bulk, dual-core processors followed by multicore processors that will further increase processing capacity while maintaining the same overhead.


This paper is intended for a technical audience of information services (IS) professionals, database administrators, and system architects interested in the performance and scalability offered by Microsoft SQL Server 2005 Standard and Enterprise Editions (64-bit). This document assumes that you have an understanding of databases in general and have some basic knowledge of Microsoft SQL Server.

Overview: Database Performance and Scalability

To make timely and informed business decisions in dynamic and competitive environments, organizations must be able to store and analyze massive amounts of business data easily and quickly. Always a critical part of the IT infrastructure, databases are at the heart of a number of converging trends in IT:

  • Applications and data are growing in complexity and size. Many applications running on 32-bit platforms today are approaching or have exceeded the limits of the platform, specifically regarding the number of processors and addressable memory.

  • Advanced DBMS capabilities, particularly in the areas of scalable architecture and high availability, have become a business necessity and are increasingly common as more organizations gather and analyze data from numerous data sources, and serve that data to growing numbers of business users.

  • Organizations are consolidating servers to simplify critical data center operations. Consolidation can reduce management complexity and cost, while reducing physical space requirements in the data center.

In anticipation of these trends, Microsoft has invested heavily in research and development and has produced 64-bit versions of its powerful SQL Server 2005 database, optimized for these processors; Intel Itanium 2, AMD Opteron, AMD Athlon 64, Intel Xeon with EM64T support, and the Intel Pentium IV with EM64T support.

By leveraging the tremendous scalability and memory addressability of the 64-bit architecture, SQL Server 2005 (64-bit) can host increasingly large and complex database and analysis applications, and support server consolidation on large-scale SMP systems with many processors. Applications using SQL Server 2005 (64-bit) databases can benefit from massive in-memory data caching data as well as larger data structures for multiple parallel workloads, concurrent user connections, plan cache, sort space, and lock memory.

By eliminating 32-bit platform and processing bottlenecks, the 64-bit platform offers a new level of scalability for business applications at an affordable cost.

SQL Server 2005 (64-bit)

SQL Server 2005 (64-bit) is optimized to run on servers using Intel Itanium 2, AMD Opteron, AMD Athlon 64, Intel Xeon with EM64T support, or Intel Pentium IV with EM64T support processors and Microsoft Windows Server 2003 Service Pack (SP) 1, offering exceptional performance and scalability. Both the 32-bit and 64-bit versions of SQL Server 2005 are based on a common architecture, providing an easy migration path for existing applications. Companies can capitalize on existing tools and expertise for new applications.

The primary differences between the 64-bit and 32-bit versions of SQL Server 2005 are derived from the benefits of the underlying 64-bit architecture. Some of these are:

  • The 64-bit architecture offers a larger directly-addressable memory space. SQL Server 2005 (64-bit) is not bound by the memory limits of 32-bit systems. Therefore, more memory is available for performing complex queries and supporting essential database operations.

  • The 64-bit processor provides enhanced parallelism, thereby providing more linear scalability and support for up to 64 processors, and yielding stronger returns per processor as compared to 32-bit systems.

  • The improved bus architecture enhances performance by moving more data between cache and processors in shorter periods.

  • A larger on-die cache allows for faster completion of user requests and more efficient use of processor time.

By taking advantage of these architectural advantages, SQL Server 2005 (64-bit) can handle large and complex query workloads, consolidate many database applications, and effortlessly scale to meet the increasing processing and performance demands of today's IT environment.
SQL Server 2005 (64-bit) hardware requirements

SQL Server 2005 (64-bit) does not have a separate hardware compatibility list (HCL). User may opt for hardware that is otherwise certified for the operating systems and meets the minimum requirements shown in Table 1.

Table 1:  Hardware Requirements

SQL Server 2005 (64-bit)

Processor type

Processor speed

Memory (RAM)

Developer Edition

IA64 minimum: Itanium I processor or higher

IA64 recommended: Itanium 2 processor

X64 minimum: AMD Opteron, AMD Athlon 64, Intel Xeon with Intel EM64T support, Intel Pentium IV with EM64T support

IA64 minimum: 733 MHz

X64 minimum: 1 GHz

IA64 minimum: 512 MB

IA64 recommended: 1 GB or more

IA64 maximum: No limit (OS restricted)

X64 minimum:512 MB

X64 recommended: 1 GB or more

X64 maximum: No limit (OS restricted).

Standard Edition

IA64 minimum: Itanium I processor or higher

IA64 recommended: Itanium 2 processor

X64 minimum: AMD Opteron, AMD Athlon 64, Intel Xeon with Intel EM64T support, Intel Pentium IV with EM64T support

IA64 minimum: 733 MHz

X64 minimum: 1 GHz

IA64 minimum: 512 MB

IA64 recommended: 1 GB or more

IA64 maximum: No limit (OS restricted)

X64 minimum:512 MB

X64 recommended: 1 GB or more

X64 maximum: No limit (OS restricted)

Enterprise Edition

IA64 minimum: Itanium I processor or higher

IA64 recommended: Itanium 2 processor

X64 minimum: AMD Opteron, AMD Athlon 64, Intel Xeon with Intel EM64T support, Intel Pentium IV with EM64T support

IA64 minimum: 733 MHz

X64 minimum: 1 GHz

IA64 minimum: 512 MB

IA64 recommended: 1 GB or more

IA64 maximum: No limit (OS restricted)

X64 minimum:512 MB

X64 recommended: 1 GB or more

X64 maximum: No limit (OS restricted)

Workgroup Edition

Not available in 64-bit editions. The 32-bit edition works in 64-bit Windows under WoW (Windows on Windows).

Express Edition

Not available in 64-bit editions. The 32-bit editions works in 64-bit Windows under WoW (Windows on Windows).

SQL Server 2005 (64-bit) can be deployed in the following configuration.

Table 2: SQL Server 2005 (64-bit) Deployment Options


Hardware vendors

Software configuration

Itanium 2 (IA64) Processors (Intel)

HP, Unisys, IBM, Dell, Fujitsu and Bull, NEC, in 4-way to 64-way configurations.

SQL Server 2005 (64-bit) IA64 and Windows 2003 SP1 64-bit operating system for IA64 systems.

x64 Processors (AMD64 and Intel EM64T)

HP, IBM, Sun, Bull and Egenera

SQL Server 2005 (64-bit) x64 and Windows 2003 SP1 64-bit operating system for x64 systems.

SQL Server 2005 (64-bit) components

What sets this release of 64-bit SQL Server apart from its predecessor is that rather than having just the core components 64-bit capable, all4 features in SQL Server 2005 are 64-bit enabled either natively (as in the case of the server engines), or through Microsoft Windows on Windows 64-bit mode (as in the case of the tools included in SQL Server Management Studio). WOW64 is a feature of the 64-bit editions of Microsoft Windows that allows 32-bit applications to execute in 32-bit mode on a 64-bit Windows operating system. Applications function perfectly in 32-bit mode even though the underlying operating system is running on the 64-bit platform. All 64-bit components are code-compatible with the 32-bit version of SQL Server 2005, making it easy to integrate a 64-bit server with other 32-bit versions of SQL Server 2005 database servers.
Advantages of the 64-bit architecture

The enhanced scalability and performance of SQL Server 2005 (64-bit) is made possible by a number of architectural features of the 64-bit architecture. Following are descriptions of each key architectural benefit.

  • Memory addressability

A 32-bit system can directly address only a 4-GB address space. Additional memory is indirectly accessible by using Address Windowing Extensions (AWE) on 32-bit platforms, as described in a later section. Windows Server 2003 SP1 running on the Intel Itanium 64-bit architecture supports up to 1,024 gigabytes of both physical and addressable memory.

  • Larger numbers of processors and more linear scalability per processor

Improvements in parallel processing and bus architectures enable 64-bit platforms to support larger numbers of processors (up to 64) while providing close to linear scalability with each additional processor. With a larger number of processors, SQL Server can support more processes, applications, and users in a single system.

Server platforms that offer more than 32 CPUs are available exclusively on 64-bit architecture. The highest TPC-C benchmark figures for SQL Server have been achieved on 64-bit systems because these systems leverage both large amounts of memory and the superior scaling of 64-bit processors on the 64-bit architecture.

  • Enhanced bus architecture

The bus architecture on current 64-bit chipsets is faster and wider than earlier generations. More data is passed to the cache and processor; this is somewhat analogous to the improvement that broadband connections offer over dial-up connections.

SQL Server 2005 (32-bit) with AWE

Microsoft SQL Server 2005 Enterprise Edition (32-bit) uses the Microsoft Windows 2003 Address Windowing Extensions (AWE) API to support more than 4 GB of memory on the 32-bit platform. This has been available since SQL Server 2000 but it is not without concerns. For some applications that use AWE, upgrading to the 64-bit platform may be a viable option. For others; it is the only way to scale.
AWE: An overview

A 32-bit server system can manage a maximum of 4 GB of memory. This limits the addressable memory space for Windows 2000 and Windows 2003 systems to 4 GB. (This is true for all 32-bit operating systems). With 2 GB reserved for the operating system by default on 32-bit Windows, only 2 GB of memory remains for the application (in this case, SQL Server 2005). You can increase this amount to 3 GB by setting a /3GB switch in a Windows boot.ini file but this is not without its own concerns (which we will discuss in the later sections).

AWE is a set of memory management extensions to the Microsoft Win32 API that allows applications to address memory beyond 4 GB. Using AWE, applications can acquire physical memory as nonpaged memory, and then dynamically map views of the nonpaged memory to the 32-bit address space. AWE enables memory-intensive applications, such as large database systems, to address larger amounts of data.

More information on AWE can be found at the Microsoft Software Developer Network!href( (MSDN) Web site (

By using AWE, a SQL Server Enterprise Edition instance can address significantly more memory than standard implementations:

  • Up to 32 GB of physical memory on Windows Server 2003, Enterprise Edition using AWE

  • Up to 64 GB of memory using Windows Server 2003, Datacenter Edition using AWE

Although AWE makes execution of memory-intensive applications possible when otherwise impossible, AWE imposes overhead, adds initialization time, and can face performance challenges under various processing conditions. These issues are eliminated on the 64-bit platform when directly addressing memory.
Limitations of AWE

The use of SQL Server 2005 (32-bit) with AWE has several important limitations. The additional memory addressability is available only to the relational database engine’s management of database page buffers. It is not available to other memory consuming database operations such as caching query plans, sorting, indexing, joins, or for storing user connection information. It is also not available on other engines such as Analysis Services. In contrast, SQL Server 2005 (64-bit) makes memory available to all database processes and operations. Using the 64-bit version on either IA64 or x64 hardware, a SQL Server instance can address up to 1 terabyte of memory; the current maximum amount of physical memory supported by Windows Server 2003 SP1. (There is a theoretical addressable limit of 18 Exabytes.) This memory is available to all components of SQL Server, and to all operations within the database engine.

As a result, SQL Server 2005 (64-bit) enhances the performance of a wide range of memory-intensive database applications.

AWE does not increase Virtual Address Space

A 32-bit system limits the virtual address space (the address space used by Windows to manage memory allocations) to 2 GB. Since AWE does not eliminate this virtual address space (VAS) limitation, many users try to raise the ceiling for this 32-bit limitation of only 2 GB of VAS by using the /3GB switch in the boot.ini file. This increases the VAS to 3 GB, thereby leaving only 1 GB for the operating system. This results in the reduction of the addressable physical memory of a single instance of Windows Server 2003 Enterprise and Datacenter editions to 16 GB. When not using the /3GB switch on Windows Server 2003 Enterprise Edition, the maximum memory addressable is 32 GB. For the Datacenter edition, it is 64 GB. This is because Windows requires more than 1 GB of VAS to manage more than 16 GB of total physical memory in one instance. So, using the switch may impose an artificial ceiling, thereby diminishing the capacity of your hardware and operating system.

For all practical purposes, the use of AWE in a 32-bit environment is only for data caching. This is because data pages use relative addressing (a requirement for AWE usage), while other components do not. Consequently, other components, operating within a relatively small VAS of either 2 or 3 GB could be significantly blocked in larger systems that have complex workloads or many concurrent users even when running on high end servers with abundant memory.

For example, the plan cache (cache of query plans) in SQL Server 2005 resides in the VAS. In cases of VAS memory pressure, query plans and execution contexts with costs of zero (0) are deleted from the plan cache. In high transaction environments, this could lead to poor performance due to the time and CPU resources that are needed to compile the query plans again. Conversely, on 64-bit systems, VAS is, for all practical purposes, unlimited. The result is faster performance because no additional time is taken up re-creating a query plan. This results in less CPU loading since the CPU is not working to compile a new plan as frequently. Such incidences can occur even on servers with large amounts of memory (such as 8 GB or more) because the plan cache (and other components except data pages) cannot take advantage of AWE memory.

Another example of the limitations of AWE concerns support in SQL Server 2005 for the common language runtime (CLR). Although the CLR uses some memory allocations from the buffer pool (single-page allocator) where AWE is most useful, most SQL Operating System (SQLOS) memory allocations (multipage allocator) on behalf of the CLR are from the VAS. For customers who are considering more than moderate use of the CLR within SQL Server 2005, an additional reason to adopt 64-bit would be to prevent loss of performance from VAS memory pressure.

Considerations for Choosing SQL Server 2005 (64-bit)

Although it offers significant scalability and performance for many applications, not every application will benefit from the 64-bit version of SQL Server. This section will help you to determine whether to use either existing SQL Server instances or to deploy new systems on the 64-bit platform.

A common request from customers who have upgraded to SQL Server 2000 64-bit on the IA64 platform would be to have the SQL Server tools available on IA64. In SQL Server 2005, most components are supported natively on IA64. In addition, both native and WOW64 support is available on the x64 platforms (Intel Xeon with EM64T and AMD64 (that is, AMD Opteron and AMD Athlon 64). This eliminates the need to run SQL Server tools on a 32-bit platform.

While the first 64-bit version of SQL Server 2000 ran solely on IA64-based servers, and was pure 64-bit, SQL Server 2000 (32-bit) SP4 on x64 servers provided an intermediate step up to the 64-bit platform. It is worthwhile to note that users can already run all SQL Server 2000 (32-bit) components on WOW64 on the x64 platform today starting with the Service Pack 4 release. On IA64, however, components such as management tools will have to be run on a separate 32-bit computer accessing the database engine on the IA64 machine. While this does not impose any major usability or performance issues, it is an inconvenience for some users.

SQL Server 2005 for both IA64 and the x64 platforms is enhanced to run on Intel- and AMD-based 64-bit servers. Customers can run SQL Server (64-bit) and all its components in native 64-bit mode. Or, they can run SQL Server (32-bit) in WOW64 mode, eliminating the need for a separate computer just to run the tools. This is an important step forward since many customers run third-party infrastructure software such as anti-virus monitors, network agents, and systems management agents on their SQL Server computers. Third-party software that might not have 64-bit support can continue to co-exist on the same 64-bit server as SQL Server 2005.

With the enhancements brought about by the 64-bit platform, SQL Server 2005 exploits these hardware gains to further improve memory and parallel processing capabilities. This results in significant gains in performance and scalability. Some scenarios that are clear winners include:

  • Demanding applications, such as SAP Advance Planning and Optimization (APO), that require large amounts of directly addressable memory will probably see significant performance gains and scalability improvements in terms of concurrent users and response time.

  • On 32-bit systems, Analysis Services is limited to 3 GB of maximum physical memory. The 64-bit platform can help eliminate this limitation. It can also help to create or accelerate large online analytical processing (OLAP) systems with rapid response time requirements.

  • The 64-bit platform facilitates the consolidation of multiple databases and applications to fewer servers. By hosting multiple databases on a single 64-bit system, you simplify management, improve storage utilization, and generally improve operational efficiency. Such consolidation efforts have limited capabilities on the 32-bit platform given the restrictions on memory availability and general absence of advanced hardware partitioning capabilities on 32-bit systems.

  • The 64-bit platform allows you to "scale up" current applications that are experiencing significant growth; migrating existing database servers that are meeting platform limitations doesn't affect the other tiers of multi-tiered applications.

  • 64-bit servers can replace legacy UNIX or mainframe systems/applications. The 64-bit platform offers a powerful and reliable alternative to UNIX/mainframe systems for high-end database servers.

The next sections list some of the factors you should consider when evaluating specific applications for the 64-bit platform.
Relational database performance factors

Memory-intensive SQL Server relational workloads are good candidates for SQL Server (64-bit). Many SQL Server resources are restricted to 2- or 3-GB memory limit in the 32-bit environment. These resources include:

  • Sort space

  • Hash tables used in joins and aggregates

  • Index creation, including full-text indexing

  • User connection memory

  • Plan cache for compiled plans

Systems starved of virtual memory exhibit degraded performance because of waits for resources and delays as the processors compile plans that have been evicted from the cache. These systems may also experience excessive disk activity to write objects. An example of this would be hash tables that cannot fit into the available memory to disk.

Very large and complex queries that cannot fit in the relatively small virtual address space available on the 32-bit platform—especially queries that are executing against data warehouses and touching large volumes of data—can be affected by resource waits caused by disk usage. With the large amount of virtual address space available in 64-bit systems, these queries can run completely in memory very quickly.

These performance gains will be noticeable even for systems that currently take advantage of AWE memory on today’s 32-bit systems because mapping memory pages in and out of the virtual address space (a function of AWE usage) requires time and multiple processor cycles. The reduction and/or elimination of this overhead will be most noticeable on systems that have large numbers of concurrent users or systems running complex queries that work with very large volumes of data.

Other operations that can benefit from extended memory include:

  • Index creation operations benefit from the existence of larger addressable memory. This is because the entire sort can be done in memory. It is not necessary to write intermediate result sets to disk prior to performing the final write to disk of the actual index.

  • Full-text indexing is restricted to either 2-GB or 3-GB workspaces for 32-bit computers. (In practice, since memory is also used for other processes, this restriction is notably lower than 2 or 3 GB.) This creates a potential bottleneck for creating or rebuilding very large Full-text indexes. Early customer deployments of very large full-text search systems show orders of magnitude gain in speed when rebuilding indexes for these systems.

  • Complex queries that use sorting or large hash joins or hash aggregates perform significantly better when sufficient directly addressable memory is available. Hash joins are very efficient, but can be memory intensive. When there is memory pressure on the system, hash joins can be removed from the cache in favor of memory-conserving, but slower, alternative query plans.

  • Systems that have large numbers of active stored procedures will benefit through improved plan caching capacity. The 64-bit architecture can substantially reduce overall CPU utilization and latency by eliminating the need to evict procedures from cache and compile frequently.

  • Server-side cursors, which are often heavy consumers of memory, can more readily be kept in memory, thereby resulting in better performance.

  • Operations such as aggregation and sorting need to work with the entire datasets. These operations can benefit from the increased memory support provided by the 64-bit platform.

Many I/O-intensive applications can benefit if they can load a larger working dataset into memory than is possible in the 64-bit environment. Although applications that require more memory than the 64 GB limit supported by AWE are rare, certain applications or workloads can benefit from the speed of extracting the database pages from extremely large cache memory instead of the disk subsystem.
Analysis Services considerations

Like Analysis Services 2000 (32-bit), Analysis Services 2005 (32-bit) is unable to take advantage of the memory extensions of AWE. It therefore is restricted to 3GB of total usable physical memory. This makes 64-bit versions of SQL Server all the more relevant for large scale enterprise business intelligence solutions that use Analysis Services.

The additional memory available on 64-bit platforms gives Analysis Services the capability of supporting very large dimensions or numerous large dimensions for faster access and processing. Consider the 64-bit environment if your OLAP application requires:

  • Very large dimensions. SQL Server 2005 (64-bit) has demonstrated support for very large dimensions.

  • Large memory use for process buffers

  • Very large cubes. Significant performance benefits for very large cubes can be achieved through the use of the larger cache, thereby reducing the need for physical disk access for base cubes or aggregate data during queries. This can benefit Analysis Services deployments that have extensive fact partitions and large numbers of aggregates.

  • Fast cube processing. Memory availability reduces the need for writing to temporary files on the disk subsystem. Additional memory also allows for more parallelization during the aggregation stage.

  • A large number of concurrent users.

Before adopting a 64-bit environment for data analysis, users need to ensure that the following requirements are met:

  • 64-bit OLE DB providers for all data sources used to populate a database in the 64-bit environment must be available. SQL Server 2005 (64-bit) includes an OLE DB provider for accessing SQL Server. If using data sources from other database vendors, users should verify the availability of suitable OLE DB providers.

  • Analysis Services user-defined functions (UDFs) or other components written in Microsoft Visual Basic® 6.0 are not supported in the 64-bit environment. Users need to verify if these components exist and if necessary rewrite them by using Microsoft Visual Studio® 2005 and then compile them using the 64-bit compiler.
Integration Services considerations

When SQL Server 2000 64-bit was released, Data Transformation Services (DTS) was not supported on a 64-bit Itanium computer. However, SQL Server 2005 Integration Services (SSIS), a complete re-architecture of DTS, is now available natively on both the 32-bit and 64-bit platforms. Additionally, the 64-bit version of SQL Server 2005 SSIS can be installed on both IA64 as well as x64 systems (EM64T for Intel and AMD64 for AMD), providing greater flexibility and choice for users on whichever platform is most suitable for their environment5.

This is especially good news since SSIS on 32-bit systems can only use virtual address space (VAS) memory (2 GB, or 3 GB if the /3GB switch is in use), making AWE memory support/availability irrelevant for SSIS.

Real-live workload tests with early adopter customers running very large databases and complex extract, transform and load (ETL) processes have yielded dramatic results. Using similarly configured 32- and 64-bit systems, tests on these workloads have shown that running SSIS packages involving reading large numbers of rows, performing aggregations, and loading results into multiple tables can have huge performance gains on the order of four times faster on 64-bit systems. This is partly due to the improve process parallelization within the 64-bit process which SQL Server 2005 64-bit takes advantage of automatically without the need for user intervention.

SSIS components on a 64-bit platform offer the following benefits:

  • SSIS components that perform row-by-row operations such as computing new columns, converting data, character conversions, and look-up joins to reference tables benefit from the enhanced performance provided by the 64-bit platform.

  • SSIS tasks that perform aggregation, sorting, and fuzzy lookups, need to work with the entire dataset and benefit from the increased memory.

  • In a traditional data warehouse loading scenario, the integration process conforms and loads the data, while the aggregation, sorting and other operations are performed by the database server. These operations contend with competing demands for resources from user queries. In addition, this architecture does not scale well for very large volumes of data and for multiple, complex aggregations. SSIS on 64-bit facilitates performing aggregations and sorting, in addition to conforming and loading the data. This architecture scales well and also frees-up the database for user queries.
Reporting Services considerations

SQL Server 2005 Reporting Services supports 64-bit processors, including the Intel Itanium2 processor and also the x64 architecture from AMD and Intel. On x64 systems, Reporting Services can run in both native 64-bit mode and also the 32-bit Windows on Windows (WOW) subsystem.

In general, 64-bit systems running at the same processor speed will not increase the throughput of reports. Instead, the primary benefit is that users can view and export the output of larger reports. You might get better throughput on 64-bit machines at higher workloads, because contention for memory will be lower and garbage collection will occur less frequently.

Server consolidation considerations

Early tests6 conducted using a popular Enterprise Resource Planning (ERP) application showed that 64-bit systems have notably improved scalability gains per CPU than their 32-bit counterparts. That is, 64-bit systems provide more linear scalability. A significant portion of this gain comes from the improvements in the bus architecture and bigger on-die cache. Furthermore, server platforms offering more than 32 CPUs are available exclusively on 64-bit architecture. The highest TPC-C benchmark results for SQL Server have been achieved on 64-bit systems leveraging both large amounts of memory and the superior scaling of 64-bit architecture. The biggest benefit here for end users is that the optimizations are built into SQL Server 2005 and the user does not need to do any extra work enjoy the benefits.

The additional processor and memory headroom available within the 64-bit environment enable significant scale-up and server consolidation opportunities. A large number of consolidated databases can fit into a single SQL instance that has sufficient memory to support the data structures (connections, locks, hash, and so on) needed for multiple coexisting applications. The same benefits also apply to consolidation of multiple instances onto a single physical server.

Users should seriously consider SQL Server 2005 (64-bit) for CPU-intensive workloads for which scalability needs can be addressed by adding additional processors. The 64-bit version is particularly valuable for SQL Server instances using 16 or more processors. Additionally, with the support for “hot-add memory” in SQL Server 2005, users can dynamically increase the processing capacity of their SQL Server systems without impacting workloads and users while doing so.

In the case of server consolidation, if one intends to bring ten databases from ten different servers onto one server, on a 32-bit server, technical limitations may force customers to install multiple instances rather than keeping all the databases in a single instance.

The reason for this is virtual address space (VAS). Remember that each of the ten original standalone instances had to use VAS for everything from lock management to plan cache. Measuring the amount of VAS memory utilization for each SQL Server instance on each server might reveal that, in total, the amount of VAS that all ten servers used can exceed the 2- to 3-GB boundary. If that boundary is ignored, then a whole host of performance problems will likely arise and impact all databases. That is why consolidating many databases from many servers into one instance on the 32-bit platform may become a problem, and thus the requirement to use multiple instances. While this is not necessarily a bad thing in itself, it does limit the options available to users when undertaking consolidation projects.

This is not an issue for 64-bit platforms since the VAS for a 64-bit system is a theoretical 18 Exabytes instead of 2 GB. Customers can decide, based on business requirements, on whether to consolidate onto a single instance or multiple instances. They are not forced down one path by technology limitations. The 64-bit platform provides greater flexibility when considering a consolidation strategy. Consolidation often provides cost savings in SQL Server processor licenses in addition to operational savings attributed to the need for fewer servers and less complexity to manage.

SQL Server 2005 (64-bit) Deployment Considerations

Microsoft has invested significant effort to provide compatibility between SQL Server 2005 (64-bit) and SQL Server 2005 (32-bit). This includes having compatible on-disk data and log file formats. The similarities between the two systems at the product-usage level (despite the complex differences at the lower, resource management level), significantly ease the process of migration, and of integrating 32-bit and 64-bit platforms in the same infrastructure.

An enterprise data center can consist of a mix of 32-bit and 64-bit systems and applications. Organizations can continue to use and purchase 32-bit servers, and connect to a 64-bit server back-end database to gain 64-bit platform benefits, or have a server farm with a mix of both. No client code changes are required to enable servicing data requests from a 32-bit or 64-bit environment. Applications that access 32-bit can connect to and access 64-bit systems without changing application code, as Transact SQL code for both versions is fully compatible. This gives users a great deal of flexibility in determining the appropriate rate of 64-bit adoption for their organizations.
Mission-critical safety net

There are a variety of add-on functionalities relating to SQL Server that businesses have grown to depend on and need to know if they will be available for the 64-bit platforms.

Audit trails, disaster recovery, backup/restore support

Many customers require an audit trail of business processes. Who changed what and when and how did they do so? SQL Server Profiler in SQL Server 2005 can be installed on 64-bit systems to provide trace functionality for audit trails. Additionally, Microsoft is working with third-party vendors such as Lumigent and LogPI to provide additional functionality based on the transaction logs.

All of the backup and restore features inherent in the 32-bit version of SQL Server 2005 are present in the 64-bit version with performance improvements.

In addition, disaster recovery features such log shipping and database mirroring, as well as failover clustering are all present in the 64-bit version of SQL Server 2005. From a user perspective, these features behave the same way as in 32-bit systems despite the additional benefits provided when run on 64-bit systems.

Third-party support for 64-bit

Although it is true there are still some vendor applications that are not yet supported on the native 64-bit platform, the new AMD and Intel x64 server releases can allow for these 32-bit applications to run unmodified (under WOW) while SQL Server 2005 can run natively (x64) or in OS emulation mode (WOW64). Vendor support for 64-bit is growing at a healthy pace with most major software vendors, including security and anti-virus software vendors, already supporting the 64-bit platform.
Compatibility issues

SQL Server 2005 (64-bit) is fully compatible with SQL Server 2005 (32-bit), enabling easy integration in existing infrastructure while providing support for the extended 64-bit hardware. The product offers complete compatibility with the SQL Server 2000 (32-bit and 64-bit) database and transaction log files.

Unlike SQL Server 2000 (64-bit), SQL Server 2005 management tools and client components are available on 64-bit either natively or in WOW.

There are a number of enhancements and component changes with the 64-bit versions of SQL Server and Windows Server 2003. Components that used to be part of SQL Server set up, such as Microsoft Data Access Components (MDAC), Distributed Transaction Coordinator (DTC), and Microsoft Management Console (MMC), are now installed as core components as part of the Windows Server 2003 set up. This enables SQL Server 2005 (64-bit) to take advantage of these operating system resources.


The migration of data from SQL Server 2000 (32-bit and 64-bit) and SQL Server  2005 (32-bit) to SQL Server 2005 (64-bit) is a straightforward task, as both share the same on-disk data and log file format. The mechanisms available include using detach and attach or backup and restore.

  • Detach/Attach

System-provided stored procedures are available to detach (sp_detach_db) the database from the 32-bit version, then attach (sp_attach_db) to the 64-bit instance. This can also be done in a GUI environment by using SQL Server Management Studio.

  • Backup/Restore

The same process for a standard backup and restore can be used to migrate data to the 64-bit platform, by simply restoring 32-bit backup files to the 64-bit platform. This can be performed by using Transact-SQL commands or via GUI tools.

It is also possible to migrate data back to the 32-bit version for SQL Server 2005 databases. However, downgrading to SQL Server 7.0 from SQL Server 2005 (64-bit) is not supported.

SQL Server 2005 can also perform the migration by upgrading an existing SQL Server 2000 64-bit database when performing an “in-place” install. Because SQL Server 2005 tools can be installed onto the 64-bit platform, it also possible to use the Copy Database Wizard (CDW) to bring a SQL Server 2000 database over from another server and attach it automatically. CDW can also script-out the SQL logins and passwords from the SQL Server 2000 installation and re-create them automatically on the destination 64-bit SQL Server. This also applies to any user-defined jobs that were related to the upgraded database.

Drivers for 64-bit

Microsoft provides 64-bit versions of all the necessary drivers for SQL Server 2005. However, third party drivers for applications and hardware should be investigated early in the process to ensure that they are either available natively, or an alternative exists.


SQL Server 2005 (64-bit) provides a highly scalable database platform for memory-intensive, performance-critical applications. The 64-bit version provides massively scalable performance for large, complex queries through:

  • Large memory addressing

  • The removal of 32-bit virtual memory limitations

  • Support for up to 64 processors in SMP systems

  • Enhanced parallelism

While many SQL Server workloads perform well in the 32-bit environment, the additional memory and processors available in the 64-bit environment are valuable in a number of situations, including:

  • Scale-up scenarios requiring 16-way or larger SMP servers.

  • Workloads with large-scale sorting, hash joins, and query memory, such as complex relational data warehouse queries.

  • Analysis Services applications with very large dimensions or large volumes of data that can take advantage of file system cache.

  • Applications that are memory-constrained in the 32-bit environment.

SQL Server 2005 (64-bit) is optimized for several 64-bit hardware solutions. Solutions from Intel with its three processor families—the Itanium 2 and both the Xeon and Pentium with EM64T 64-bit memory extensions—are fully supported. SQL Server 2005 64-bit is also supported on AMD’s Athlon64 and Opteron processors. All these processors take advantage of advanced memory addressing capabilities for essential resources such as buffer pools, caches, and sort heaps, reducing the need to perform multiple I/O operations to bring data in and out of memory from disk. This greater processing capacity without the penalties of I/O latency provides a mechanism to achieve new levels of application scalability without the necessity of changing application code.

SQL Server 2005 (64-bit) achieves these gains in performance and scalability while maintaining tight integration with existing products and applications plus offering a simple migration path. Organizations can use 32-bit application servers connected to 64-bit database servers, phasing in the 64-bit technology as appropriate. SQL Server 2005 (64-bit) can also integrate easily into an existing database server infrastructure with other 32-bit databases.

SQL Server 2005 (64-bit) can directly address the maximum memory supported by Microsoft Windows Server 2003 SP1 (currently 1 terabyte). Using 64-bit servers that have large amounts of memory, SQL Server 2005 (64-bit) can load and process very large databases in only a fraction of the time than what is required in a 32-bit environment.

While there may be no urgency to replace 32-bit systems that are currently performing adequately, customers are highly encouraged to consider the 64-bit platform in all new deployments and planned hardware upgrade cycles. Given the direction of the industry on server systems, 64-bit systems will be the standard rather than the exception in the next two to three years, if not sooner. With automated resource management capabilities built into SQL Server, customers can expend little or no effort to take maximum advantage of this new generation of hardware to get better scalability, business continuity, and lower costs.


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1TPC-C Throughput: 1,082,203, Price/Performance: 5.38 US dollars, Database Manager: Microsoft SQL Server 2005 Enterprise Edition 64-bit, Hardware:HP Integrity Superdome 64P c/s, Availability Date: 12/07/05.


2 “Prepare for the Arrival of Dual-Core Processors,” by Martin Reynolds, Gartner Researche 27 April 2005. URL:

3 Complete case study available at the Microsoft Global Evidence Management Web site at:

4 x64 version supports all the features of SQL Server 2005. Itanium supports most features. Itanium does not support developer tools hosted in the Visual Studio shell.

5 SQL Server Integration services packages can execute on both X64 and Itanium platforms. They, however, cannot be developed or debugged on an Itanium platform.


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