MVS™ provides installation exits to allow further processing of messages and commands. Whenever these exits are active and the system issues a message, or an operator or program issues a command, the exits get control to process the message or command. For messages, MVS provides IEAVMXIT, which allows you to tailor your messages. You can also install your own message processing exits as needed. For commands, MVS provides the command installation exit that can accept, modify, or reject commands before the command processor for the command gets control.

Allocation exits can get control whenever the system issues WTOR messages to operators to cancel a waiting job, bring a device online, or allow a job to wait. These exits allow an installation to automate responses to the messages. For more information on allocation exits, see z/OS MVS Installation Exits.