Mainframe, MVS and zOS Discussion

Hi ,

I'm not sure what answer is best suitable when someone asks :: When should we go for COMP,COMP-3 variables? What advantage these variables have over Usage DISPLAY variables other than Memory size?

COMP and COMP-3 variables are best when doing arithmetic with the variables. COMP works better for indexing / subscripting while COMP-3 is typically how COBOL does mathematical operations. However, the difference between these variables and zoned decimal variables will be negligible unless you are doing BILLIONS of operations in your program.

Robert Sample wrote: However, the difference between these variables and zoned decimal variables will be negligible unless you are doing BILLIONS of operations in your program.

What difference you're talking about here?

Using COMP variables for subscripts and COMP-3 variables for arithmetic is SLIGHTLY more efficient (less CPU time) than zoned decimal. However, to see any CPU difference in COMP / COMP-3 versus zoned decimal, you have to be doing a LOT of calculations / subscripts. In general, unless you have a known issue with performance, you could code your program without any COMP / COMP-3 variables and you would not see any difference in CPU time.

Thanks you Robert.

In a recent interview I told the same to the interviewer but he asked leave it and in general how the "amount filed" will be defined comp or comp-3...

An amount field implies accumulation and / or arithmetic so use COMP-3.