Microsoft KB Archive/283217

= Registry Hive Fragmentation Fix May Cause Excessive SAM Registry Hive Size =

PSS ID Number: 283217

Article Last Modified on 10/16/2002

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The information in this article applies to:


 * Microsoft Windows NT Server 4.0 SP5
 * Microsoft Windows NT Server 4.0 SP6
 * Microsoft Windows NT Server 4.0 SP6a
 * Microsoft Windows NT Server, Enterprise Edition 4.0 SP5
 * Microsoft Windows NT Server, Enterprise Edition 4.0 SP6
 * Microsoft Windows NT Server, Enterprise Edition 4.0 SP6a

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This article was previously published under Q283217



IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:

256986 Description of the Microsoft Windows Registry



SYMPTOMS
The SAM registry hive size in Windows NT 4.0 may increase rapidly after you update your computer with Service Pack 5 (SP5), Service Pack 6 (SP6), or Service Pack 6a (SP6a).



CAUSE
This problem can occur because the Windows NT 4.0 registry cell allocation behavior reduces SAM fragmentation. This behavior is described in the following Microsoft Knowledge Base article:

197632 Registry Hive Fragmentation Leads to Excessive Size

Although this fix does help to resolve this problem, the fix can increase the SAM size in some situations where there is an excessive number of global groups with many members that rarely change. In this environment, the updated behavior of over-allocating to create larger cells that can be reused for future growth does not work and actually orphans larger fragments, which leads to excessive SAM sizes.



RESOLUTION
A supported fix is now available from Microsoft, but it is only intended to correct the problem that is described in this article. Apply it only to computers that are experiencing this specific problem. This fix may receive additional testing. Therefore, if you are not severely affected by this problem, Microsoft recommends that you wait for the next Windows NT 4.0 service pack that contains this fix.

To resolve this problem immediately, contact Microsoft Product Support Services to obtain the fix. For a complete list of Microsoft Product Support Services phone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/default.aspx?scid=fh;EN-US;CNTACTMS

NOTE: In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The typical support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

The English-language version of this fix should have the following file attributes or later:   Date        Time    Size      File name     Platform 01/03/2001 05:18p  936,640   Ntoskrnl.exe  Intel



STATUS
Microsoft has confirmed that this is a problem in Windows NT 4.0 SP5.



MORE INFORMATION
WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

NOTE: The fix referenced in this article configures SAM cellsize allocation to the original algorithm, but does not enable the user to configure RegistryAdjustCellSize. The fix to allow the registry change described below is included in the following hotfix and should be applied if you need to alter the algorithm behavior. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

294345 Registry Hive Fragmentation Behavior Is Not Configurable

A registry setting is added to Ntoskrnl.exe to make the Q197632 allocation granularity change optional. To disable the Q197632 allocation granularity setting:  Click Start, click Run, type regedit32 in the Open box, and then press ENTER. Locate and click the following registry key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control

 On the Edit menu, click Add Value, and then add the following registry value:

Value name: RegistryAdjustCellSize

Data type: REG_DWORD

Radix: Hexadecimal

Value: 0x0 revert to original hive cell allocation granularity, 0x1 use Q197632 hive cell allocation granularity.

Default: 0x1

 Quit Registry Editor.</li> Restart your computer.</li></ol>

Additional query words: ntoskrnl 283217

Keywords: kbbug kbQFE kbRegistry KB283217

Technology: kbWinNT400search kbWinNTS400search kbWinNTS400sp5 kbWinNTS400sp6 kbWinNTsearch kbWinNTSEnt400sp5 kbWinNTSEnt400sp6 kbWinNTSEnt400SP6a kbWinNTSEntSearch kbWinNTSsearch

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