The ZENworks agent version 11 SP2 and higher will cache the DN of user objects after a user logs into a device. The next time the user logs into that device, instead of searching the tree for the user ID, it will attempt to use the previous DN of the user object for authentication. If the object no longer exists, it will search the tree to see if the object has been moved. The reduced number of searches for user DNs will help reduce the overall LDAP overhead.