IMS DC MFS Control Blocks (3 of 3)

Refer my part-1 if you miss it. This post I am just explaining how these 4 control blocks align together.

When data entered on the screen, MID and DIF control blocks translate the data in the way IMS program understands. I hope so far my explanation has given good understanding on the 4 control blocks.

Let us see an example:

Input message:

PAYDET FIRST LAST EMPID

Here “PAYDET” is the transaction code

FIRST==> First Name

LAST==> Last Name

EMPID==> Employee ID, however, from which logical terminal this message is coming will not appear in the message, but it will be captured in the first field of I/O PCB mask.

Example of output message:

LLZZFIRST LAST XXXXXXXXXXXX

Here, LL ==> length of the message PIC S9(4) Comp if it is in COBOL.

If PL1 is there it is PIC S9(8) Comp.

ZZ ==>2 byte field MFS formatting option.