If a UNION appears as a subquery or derived table and the UNION contains parameters or local variables, the connection will get an access violation (AV). You will receive an error message similar to the following:

The following errors might be seen when creating merge subscriptions: When the next identity value for MSmerge_agents is greater than 999 sp_addmergesubscription fails.

A query that contains a correlated subquery with an OR EXISTS clause may perform slowly.