Mainframe Tutorial
JCL Tutorial
Introduction
Mainframe Interview Q&A
Mainframe Quiz
Mainframe Memes
Contact us
About usModule 11:- Library Facility and sub-programming
Backward
Types of call
- When any modification is made in sub-program, it needs to be recompiled.
- In such case, need of recompilation of calling program (main program) is decided based on compiler option used
- Depending on the compiler option used to compile program, the calls to sub-program are categorized into two types:-
- Static call
- Dynamic call
Static call
- When calling program (main program) is compiled using NODYNAM compiler option (default), recompilation of calling program is needed to accommodate any modification of sub-program
- Calls made in such configurations is referred to as static calls.
- This kind of call occupies more memory as one executable load contains both calling and called program
Dynamic call
- When calling program (main program) is compiled using DYNAM or NODLL compiler option, recompilation of calling program is not needed to accommodate the modifications of sub-program
- This is because the modified sub-program will be in effect during the run
- Calls made in such configuration are referred to as Dynamic call
- Since called program is loaded from load library during run-time, it occupies less memory
Difference between Static call and Dynamic call
| Static call | Dynamic call |
|---|---|
| When sub-program is modified, sub-program and all its calling (main) program needs to be recompiled | When sub-program is modified, only sub-program needs to be recompiled |
| Sub-programs are link-edited(merged) with calling program during compilation of calling program | Sub-program and calling programs are compiled and link-edited separately. Sub-program will be picked from load library during run time |
| NODYNAM compiler option is used (By default) | DYNAM or NODLL compiler option is used |
|
You can identify call as static if CALL is coded like:-
CALL ‘SUBPGM’.
Here, SUBPGM is literal (value).
|
You can identify call as Dynamic, if call s coded like:-
01 MODULE-1 PIC X(8) VALUE ‘SUBPGM’.
CALL MODULE-1.
Here, MODULE-1 is identifier.
|
| Since one execution load contains both calling and called programs, it occupies more memory | Since called program is loaded from load library during run time, it occupies less memory |
| Sub-program will not be in initial state the next time it is called, unless you explicitly use INITIAL or you do a CANCEL after each call. | Program will be in initial state every time it is called |
| Fast, less flexible | Slow compared to static call. However, its more flexible |
| Preferred when program functionality does not involve frequent changes | Preferred when program functionality involves frequent changes |