I was reading about the (readmin /showrepl) command prompt and saw this: DSA InvocationID changes when application partition are rehosted. What does that mean. Luai Alrantisi, BSc in Computer Engineering, University of Ottawa 2007, Canada. IT Manager of MTN Mobile Telecom.

Here are some Technet articles which answer the question for you: The Active Directory database has its own GUID, which the DSA uses to identify the database instance (version of the database). The database GUID is stored in theinvocationId attribute on the NTDS Settings object. Unlike the DSA GUID, which never changes for the lifetime of the domain controller, the invocation ID is changed during an Active Directory restore process to ensure replication consistency. For more information about replication following a restore process, see Active Directory Replication on a Restored Domain Controller later in this section. How the Active Directory Replication Model Works And here is an article that describes why you would want to unhost/rehost an application partition: A lingering object is an object that is present on one replica, but on another replica it has been deleted and removed from the directory by the garbage collection process. When lingering object exists only in one or more read-only naming contexts (global catalog), it makes it all the more difficult to delete the object. Clearing the IS_GC bit may not always be appropriate, because it removes all read-only naming contexts from the global catalog server. Unhosting and rehosting a read-only naming context is therefore sometimes considered to be a good solution, especially because you could specify the source to be a good replica that does not contain lingering objects. Repadmin Requirements, Syntax, and Parameter Descriptions