In most cases, you can update agents on Mac OS X computers by simply installing the new agent either directly or remotely on top of an existing agent. As a best practice, you should perform in-place upgrades using a local Mac administrative (admin) account or any other user account that has local administrative rights and reboot the computer after completing the upgrade. In most cases, you should not perform the upgrade while you are logged on as an Active Directory user in a currently active session.
In rare cases, you might be advised to run adflush to clear the Active Directory cache before performing an in-place upgrade. For example, if you are updating agents from version 4.x, or earlier, to 5.1.x, run adflush first to ensure a smooth upgrade. It is highly unusual for an upgrade to require you to leave and rejoin a managed Mac computer to the domain.