Symantec recommends that you disable hierarchy replication on each adjacent hierarchy node. This step prevents any replication data from being sent to a Notification Server computer while it is mid-way through a migration. You need to disable replication on the local server that you are about to migrate. You also must disable replication on any parent and any child Notification Server computers (those that are directly before or after the local server). By completing this step, you prevent the local server from carrying out any of its usual replication jobs.

When the Notification Server computer migration has completed, you need to enable hierarchy replication again. Repeat the procedure and select Enable Replication from the context menu. Replication resumes as normal.

See Migrating Notification Server computers in a hierarchy