Link level security using a message exit

A message exit can be used only on a message channel, not on an MQI channel. It has access to both the transmission queue header, MQXQH, which includes the embedded message descriptor, and the application data in a message. It can modify the contents of the message and change its length.

A message exit can be used for any purpose that requires access to the whole message rather than a portion of it.

Message exits can be used to provide identification and authentication, access control, confidentiality, data integrity, and non-repudiation, and for reasons other than security.