What is a user exit in mainframes?

[Dilip Prasad]

Hi,

I have heard about "user exits" in mainframes, sometime like if in a SORT it won't work write a user exit. If in COBOL, it does not work write a user-exit. What exactly is a user exit? When do we need it and how do I learn to write one? Please guide if there is a step by step guide for it.

[enrico-sorichetti]

it is part of a programming standard where at certain point of the process
the control is given to a user program do do something that the original program cannot do.

each program/product will provide in the manuals the description of the user exits available
with the description of the purpose of the exit, and the calling conventions

[Dilip Prasad]

it is part of a programming standard where at certain point of the process
the control is given to a user program do do something that the original program cannot do.

each program/product will provide in the manuals the description of the user exits available
with the description of the purpose of the exit, and the calling conventions

Will there be a specific language required for the exit program in mainframes? Or we can write them in any language?

[enrico-sorichetti]

Will there be a specific language required for the exit program in mainframes?

the manuals will tell the languages that can be used for exits.

[Dilip Prasad]

Thanks enrico.

[Robert Sample]

Most system user exits are written in Assembler as they need to be small and fast. I've seen more than one SORT user exit coded in COBOL (E35 usually but sometimes others).