Enquiry applications

 

A typical WebSphere MQ application initiating an inquiry or update works as follows:

• Gather data from the user

• Put one or more WebSphere MQ messages

• Get the reply messages (you might have to wait for them)

• Provide a response to the user

Because messages put on to WebSphere MQ queues do not become available to other WebSphere MQ applications until they are committed, they must either be put out of syncpoint, or the IMS™ application must be split into two transactions.

If the inquiry involves putting a single message, we can use the no syncpoint option; however, if the inquiry is more complex, or resource updates are involved, you might get consistency problems if failure occurs and you do not use syncpointing.

To overcome this, we can split IMS MPP transactions using MQI calls using a program-to-program message switch; see IMS/ESA Application Programming: Data Communication for information about this. This allows an inquiry program to be implemented in an MPP:

 Initialize first program/Connect
  .
 Open queue for output
  .
 Put inquiry to WebSphere MQ queue
  .
 Switch to second WebSphere MQ program, passing necessary data in save
 pack area (this commits the put)
  .
END
  .
  .
 Initialize second program/Connect
  .
 Open queue for input shared
  .
 Get results of inquiry from WebSphere MQ queue
  .
 Return results to originator
 .
END

 

Parent topic:

MQI calls in IMS applications

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