How to Determine if Full Synchronizations Are Caused By Wrapping the Change Log (244396)


The information in this article applies to:

  • Microsoft Windows NT Server 4.0
This article was previously published under Q244396
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

SUMMARY

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

MORE INFORMATION

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)

Modification Type:MajorLast Reviewed:8/28/2002
Keywords:kbinfo KB244396
©2002 Microsoft Corporation. All rights reserved.