AD Replication Parameters

by Wayne Maples [Published on 20 April 2004 / Last Updated on 20 April 2004]

When a change takes place in Active Directory, there is a builtin delay before the other domain controllers are notified that replication needs to occur. This holdback time prevents constant replication activity. It determines the delay between the change to the Active Directory and first replication partner notification. The default is 300 seconds, that is 5 minutes. If this interval is set too high, directory consistency could be compromised. Too many changes are accumulated before being replicated. It is probably best to leave this setting alone, but if you need to increase the holdback interval to optimize replication performance, you use the following hack:

Hive: HKEY_LOCAL_MACHINE
Key: SYSTEM\CurrentControlSet\Services\NTDS\Parameters
Name: Replicator Notify Pause After Modify
Type: REG_DWORD

If you have broadband, Microsoft has a 2 hour series of Webcasts on Active Directory Replication:

Once a replication notification starts, the domain controller with changes doesn't notify all replication partners at once. Instead, it notifies the first replication partner and waits for 30 seconds by default, then notifies the next partner, and so on. This prevents all replication partners from requesting copies of the changes at the same time and thus prevents overloading the network. This is the Replicator Notify Pause Between DSAs parm and it can be modified using the following hack:

Hive: HKEY_LOCAL_MACHINE
Key: SYSTEM\CurrentControlSet\Services\NTDS\Parameters
Name: Replicator Notify Pause Between DSAs
Type: REG_DWORD

W2K sets the remote procedure call (RPC) replication port dynamically. For debug purposes, you might want to manually set the port. You can use the following hack:

Hive: HKEY_LOCAL_MACHINE
Key: SYSTEM\CurrentControlSet\Services\NTDS\Parameters
Name: TCP/IP Port
Type: REG_DWORD
Set to the port you want to monitor. Reboot. Be sure to remove this registry key after monitoring, or you will be compromising your security with a static RPC port.

The Knowledge Consistency Checker (KCC) manages connection objects for inter- and intrasite replication. KCC runs every 15 minutes by default. To change this time period use the following hack:

Hive: HKEY_LOCAL_MACHINE
Key: SYSTEM\CurrentControlSet\Services\NTDS\Parameters
Name: Repl topology update period (secs)
Type: REG_DWORD
and set the value.

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