Q244396: Determining if Full Syncs Are Caused By Wrapping the Change Log

Article: Q244396
Product(s): Microsoft Windows NT
Version(s): winnt:4.0
Operating System(s): 
Keyword(s): 
Last Modified: 11-JUN-2002

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The information in this article applies to:

- Microsoft Windows NT Server version 4.0 
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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:

  Q256986 Description of the Microsoft Windows Registry

SUMMARY
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There may be situations where you want to determine why backup domain
controllers (BDCs) request full synchronizations.

MORE INFORMATION
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Full synchronizations can be caused by several things:

- Using the Portuas tool

- Using the Nltest tool

- Using the net accounts /sync command

- Wrapping the change log


The only item above that can occur by itself is wrapping the change log. You can
use the checked build of the Netlogon.dll file to determine if the change log
was wrapped.

To log enough information to determine if the change log was wrapped, set the
following parameter in the registry:

  HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Netlogon\Parameters

  Value Name: DBFlag
  Data Type: REG_SZ
  String: 0x20000108 (hex)

The following lines show that a full synchronization was caused by wrapping the
change log:

  

  10/20 16:53:53 [SYNC] NetrDatabaseDeltas: SAM partial sync called by <BDC_Name> SerialNumber:0 7c7d.

  10/20 16:53:53 [CRITICAL] NetrDatabaseDeltas: delta not found in cache, returning full required.

The first line represents a particular BDC requesting all new changes. In this
example, the BDC had changes up to 0 7c7d, or the first 31,869 changes to the
Security Accounts Manager (SAM).

The second line shows that the requested delta is no longer in the change log.
The primary domain controller (PDC) ignores the partial request and tells that
BDC to request a full synchronization.

You can change the size of the change log from 64 KB to 4.19 MB. Each change
averages 32 bytes, so the change log can store approximately 2,000-130,000
changes.

To change the size of the change log:

1. Start Registry Editor (Regedit.exe).

2. Locate the following registry key:

  HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NetLogon\Parameters

3. On the Edit menu, click Add Value, and add the following value:

  Value Name: ChangeLogSize
  Data Type: REG_DWORD
  String: 0x400000 (hex)


Additional query words: synchronization 5713

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Keywords          :  
Technology        : kbWinNTsearch kbWinNT400search kbWinNTSsearch kbWinNTS400search kbWinNTS400
Version           : winnt:4.0
Issue type        : kbinfo

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