The IMS extension to the Credit Check sample on z/OS

A version of the checking-account program is supplied as an IMS batch message processing (BMP) program. It is written in the C language.

The program performs the same function as the CICS version, except that to obtain the account information, the program reads an IMS database instead of a VSAM file. If you replace the CICS version of the checking-account program with the IMS version, you see no difference in the method of using the application.

1. Follow the steps in Preparing and running the Credit Check sample on z/OS.
2. Follow the steps in Preparing the sample application for the IMS environment on z/OS.
3. Alter the definition of the alias queue CSQ4SAMP.B2.OUTPUT.ALIAS to resolve to queue CSQ4SAMP.B3.IMS.MESSAGES (instead of CSQ4SAMP.B3.MESSAGES). To do this, we can use one of:
   • The IBM MQ for z/OS operations and control panels
   • The ALTER QALIAS command .

Another way of using the IMS checking-account program is to make it serve one of the queues that receives messages from the distribution program. In the delivered form of the Credit Check sample application, there are three of these queues (B5/6/7.MESSAGES), all served by the agency-query program. This program searches a VSAM data set. To compare the use of the VSAM data set and the IMS database, you could make the IMS checking-account program serve one of these queues instead. To do this, we must alter the definition of the namelist CSQ4SAMP.B4.NAMELIST to replace one of the CSQ4SAMP.B n.MESSAGES queues with the CSQ4SAMP.B3.IMS.MESSAGES queue. We can use one of:

• The IBM MQ for z/OS operations and control panels
• The ALTER NAMELIST command.

We can then run the sample from CICS transaction MVB1. The user sees no difference in operation or response. The IMS BMP stops either after receiving a stop message or after being inactive for five minutes.

Design of the IMS checking-account program (CSQ4ICB3)

This program runs as a BMP. Start the program using its JCL before any IBM MQ messages are sent to it.

The program searches an IMS database for the account number in the loan request messages. It retrieves the corresponding account name, average balance, and credit worthiness index.

'Response from CHECKING ACCOUNT for name : JONES J B'
'   Opened 870530, 3-month average balance = 000012.57'
'   Credit worthiness index - BBB'

When running as a message-oriented BMP, the program drains the IMS message queue, then reads messages from the IBM MQ for z/OS queue and processes them. No information is received from the IMS message queue. The program reconnects to the queue manager after each checkpoint because the handles have been closed.

When running in a batch-oriented BMP, the program continues to be connected to the queue manager after each checkpoint because the handles are not closed.