After installing r18.5, user exits 17 and 18 are no longer implemented.
The IDMS r18.0 (and earlier) RHDCUXIT contained the following #DEFXIT entries:
From 18.5 and all future releases, they are commented out:
#DEFXIT , EXIT 17 - INPUT DATASTREAM IDMS/4511
* #DEFXIT MODE=SYSTEM,CALL=DC,EP=X17STUB IDMS/4511
#DEFXIT , EXIT 18 - OUTPUT DATASTREAM IDMS/4511
* #DEFXIT MODE=SYSTEM,CALL=DC,EP=X18STUB IDMS/4511
Release: r18.5 and all future releases.
X17STUB and X18STUB were sample exits. Exits 17 & 18 are used to examine and/or manipulate data streams. Exit17 is invoked for input data stream, before they are turned over to programs. Exit18 is invoked for output data streams, before they are displayed on terminals.
Prior to r18.5, they were implemented by default into RHDCUXIT during the install/configuration process. Those default implementations did not actually do anything. They were there to illustrate how user exits could be implemented in general.
From r18.5, they have been removed from RHDCUXIT as it seems clients reported performance problems with zIIP processing due to swapping from TCB to SRB and back when these two exits were called. Thus EXIT 17 and EXIT 18 were removed as defaults in RHDCUXIT for r18.5.
This change was documented internally as problem IDMS/4511 and was implemented in source in the initial r18.5 release. There was never any PTF.
If a client needs to implement EXIT 17 and EXIT 18 input and output datastream exits, they must implement them via the #DEFXIT that is contained in the RHDCUXIT sample.
This change should only affect DBCS, FACOM, HITACHI or CASDATA clients using those product exits.