Exactly 2 years completed starting this blog. Nowhere people getting correct info on IMSDC. I am trying to give good content on IMSDC.
I hope it will be helpful.
You know, in CICS, so many terminal control programs will participate when you initiate a transaction. Similarly, In IMSDC 4 control blocks will be involved when you start a transaction.
Message Output Descriptors (MODs)
Define the layout of messages MFS receives from the application program.
Device Output Formats (DOFs)
Describe how MFS formats messages for each of the devices the program communicates with.
Device Input Formats (DIFs)
Describe the formats of messages MFS receives from each of the devices the program communicates with.
Message Input Descriptors (MIDs)
Describe how MFS further formats messages so that the application program can process them.
We define these 4 control blocks in MFS macros.
In the screen, when we enter /FORMAT PAYDAY1, first IMS locates MOD with the name PAYDAY1 , and displays a screen with this name.
DOF decides, based on transaction code, and sends the required format of screen to the terminal. Means, what are the fields user should fill to get a response.
More details refer my part-2.