This stub is linked to the calling program, passes on the request to the IMS system, and returns the results and a status code.
Other types of PCB are used to send and receive transaction processing messages, access and write to the user’s VDU screen, and to print reports, etc.
This would typically contain the segment type required and the contents of any key fields.
For all languages except PL/I, the first parameter in a call is the Function Code – a four-character field, examples being: “GU ” (Get Unique), “GN ” (Get Next), “REPL” (Replace), and “ISRT” (Insert).
The program would then automatically wait till the requested data were retrieved and placed in the Segment-Area.