Performance impact of defining a numbered exit EP= vs NAME=

Products

• IDMS

Issue/Introduction

What is the performance difference, if any, between these two alternative RHDCUXIT definitions? 

#DEFXIT MODE=SYSTEM,CALL=DC,NAME=USRXIT27
#DEFXIT MODE=SYSTEM,CALL=DC,EP=UX27EP1,AMODE=ANY

Environment

Release: All supported releases.

Resolution

When defining a numbered exit in RHDCUXIT with EP=, an entry point is specified and the exit module is hard linked with RHDCUXIT. The exit is loaded at startup when RHDCUXIT and other nucleus modules are loaded. 

If the exit is instead defined with NAME=, the exit program must be linked as a load module into a CDMSLIB loadlib and must be defined as a PROGRAM in sysgen. The first time the exit is called, it is loaded.

If the program pools have been properly sized (in this case it would be the XA Reentrant Pool) then no program would ever need to be loaded more than once and would stay loaded. There should be no noticeable performance difference due to having to do the one and only load of the exit module. 

Also, using NAME= provides more flexibility if the exit ever needs to change. Only the exit needs to be reassembled/linked and then DCMT V PRO xxxxxx NC instead of having to relink RHDCUXIT and a Nucleus Reload or CV recycle.

Additional Information

Numbered Exits