Design of the sample Message Handler sample on z/OS
This topic describes the design of each of the programs that make up the Message Handler sample application.
Object validation program
This requests a valid queue and queue manager name.
If we do not specify a queue manager name, the default queue manager is used, if available. Only local queues can be used; an MQINQ is issued to check that the queue type and an error is reported if the queue is not local. If the queue is not opened successfully, or the MQGET call is inhibited on the queue, error messages are returned indicating the CompCode and Reason return code.
Message list program
This displays a list of messages on a queue with information about them such as the putdate, puttime, and the message format.
The maximum number of messages stored in the list is 99. If there are more messages on the queue than this, the current queue depth is also displayed. To choose a message for display, type the message number into the entry field (the default is 01). If your entry is not valid, you receive an appropriate error message.
Message content program
This displays message content.
The content is formatted and split into two parts:
- Message descriptor
- Message buffer
The message descriptor shows the contents of each field on a separate line.
The message buffer is formatted depending on its contents. If the buffer holds a dead letter header (MQDLH) or a transmission queue header (MQXQH), these are formatted and displayed before the buffer itself.
Before the buffer data is formatted, a title line shows the buffer length of the message in bytes. The maximum buffer size is 32768 bytes, and any message longer than this is truncated. The full size of the buffer is displayed along with a message indicating that only the first 32768 bytes of the message are displayed.
The buffer data is formatted in two ways:
- After the offset into the buffer is printed, the buffer data is displayed in hexadecimal.
- The buffer data is then displayed again as EBCDIC values. If any EBCDIC value cannot be printed, it prints a period (.) instead.
We can enter D for delete, or F for forward into the action field. If you choose to forward the message, the forward-to queue and queue manager name must be set correctly. The defaults for these fields are read from the message descriptor ReplyToQ and ReplyToQMgr fields.
If you forward a message, any header block stored in the buffer is stripped. If the message is forwarded successfully, it is removed from the original queue. If you enter invalid actions, error messages are displayed.
An example help panel called CSQ4CHP9 is also available.
Parent topic: The Message Handler sample on z/OS