Registry Hive Fragmentation Leads to Excessive Size (197632)
The information in this article applies to:
- Microsoft Windows NT Workstation 4.0
- Microsoft Windows NT Server 4.0
- Microsoft Windows NT Server, Enterprise Edition 4.0
This article was previously published under Q197632 SYMPTOMS
Processes that use the registry to repeatedly modify the same values in
small increments can cause excessive memory fragmentation in the
corresponding registry hive. The sum of the fragmented cells can become so
large that the hive size winds up many times larger than the sum of actual
data in the hive. Eventually, the sum of the hive will exceed the Registry
Size Limit (RSL), causing subsequent modifications to fail until the RSL is
increased. As an example consider the SAM hive used to store Windows NT
accounts. The SAM size frequently exceeds projected sizes due to the fact
that it fragments the SAM hive when adding members to large groups.
CAUSE
In the SAM example, when a user is added to a large group it causes the
registry value for that group to be replaced and the old value added to a
hash of free lists by size of allocation. The freed cell is coalesced with
the nearest neighbor cell in memory, if it's a free cell, to create a
slightly larger cell to add to the free lists. Over several additions, the
free lists can contain several cells that are never used because they're
too small. Over time the sum of the free cells become so large that the sum
of the hives exceeds RSL.
RESOLUTION
To resolve this problem, obtain the latest service pack for Windows NT 4.0 or
the individual software update. For information on obtaining the
latest service pack, please go to:
For information on obtaining the individual software update, contact Microsoft
Product Support Services. For a complete list of Microsoft Product Support
Services phone numbers and information on support costs, please go to the
following address on the World Wide Web:
STATUS
Microsoft has confirmed this to be a problem in Windows NT version 4.0. This problem was first corrected in Windows NT version 4.0 Service Pack 5.
| Modification Type: | Minor | Last Reviewed: | 9/23/2005 |
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| Keywords: | kbHotfixServer kbQFE kbbug kbfix kbQFE KB197632 |
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