System i: Programming Message Handling APIs - IBM

Message Handling APIs
The message handling APIs can be used to work with i5/OS ®
messages. They allow you to perform the
following tasks:
v Send messages to users or programs.
v Receive messages from a message queue.
v Handle errors.
v Return message and message queue information.
v Return message description and message file information.
Before you use the message handling APIs, read the following topics:
v “Message Handling Terms and Concepts” on page 196. This topic briefly describes the elements of
i5/OS messages and message handling.
v Control language. For complete background information, see the topic collection about messages.
The message handling APIs are:
v “Change Exception Message (QMHCHGEM) API” on page 3 (QMHCHGEM) changes an exception
message on a call message queue. This API allows the current program to perform a variety of actions
on an exception message that was sent to its caller, a previous caller, or itself.
v “Control Job Log Output (QMHCTLJL) API” on page 6 (QMHCTLJL) controls the production of a job
log when the related job ends or when the job message queue becomes full and the print-wrap option
is in effect for the job.
v “List Job Log Messages (QMHLJOBL) API” on page 13 (QMHLJOBL) lists messages from the job
message queue of a job. This function gets the requested message information and returns it in a user
space in the format specified in the parameter list.
v “List Nonprogram Messages (QMHLSTM) API” on page 30 (QMHLSTM) lists messages from one or
two nonprogram message queues. This function gets the requested message information and returns it
in a user space in the format specified in the parameter list.
v “Move Program Messages (QMHMOVPM) API” on page 48 (QMHMOVPM) moves messages from one
call message queue to the message queue of an earlier call stack entry in the call stack. This is
especially useful for error handling.
v
“Open List of History Log Messages (QMHOLHST) API” on page 54 (QMHOLHST) provides
information about messages that were sent to the QHST message queue.
v “Open List of Job Log Messages (QGYOLJBL) API” on page 65 (QGYOLJBL) lists messages from a job
log. Returned messages are sorted by their sending date and time unless the message being listed is a
reply message to an inquiry, a sender’s copy, or a notify type of message.
v “Open List of Messages (QGYOLMSG) API” on page 77 (QGYOLMSG) provides information on
messages for the current user, a specific user, or one specific nonprogram message queue.
v “Promote Message (QMHPRMM) API” on page 91 (QMHPRMM) promotes an escape or status
message that was sent to a call stack entry. That is, the message is handled and replaced with a new
escape or status message. You may promote an escape message to another escape message or to a
status message. You may promote a status message to an escape message or to another status message.
v “Receive Nonprogram Message (QMHRCVM) API” on page 94 (QMHRCVM) receives a message from
a nonprogram message queue, providing information about the sender of the message as well as the
message itself. This API is similar in function to the Receive Message (RCVMSG) command with the
MSGQ parameter.
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