Output from the Message exit

At return, restore the contents of all registers. Do not set a return code in register 15.

The exit can set these fields in the ANFUEXTP control block:
XTPMSGFL
Flag indicating whether IP PrintWay™ writes the message. IP PrintWay sets this flag to B'0' before it calls the exit.
Flag meaning when set to B'1':
XTPM2MDS
Write the message to the IP PrintWay message-log data set.
XTPMSGLN
Length of the message whose address is in field XTPMSGP.
XTPMSGP
Address of the message to be sent. This message has a message ID, followed by the message text.