COBOL z/OS Performance Improvements

COBOL tips for performance improvements

• Always consider using SEARCH ALL option instead of checking long table by coding.
• Internal SORT is usually uses longer CPU than External SORT.
• Always consider using Evaluate, it creates program more modular.
• Avoid using go to statement as they create irregular flow.
• Initializing field is more efficient as follows:

INITIALIZE WS-CHARC with SPACES

INITIALIZE WS-NUMERIC with ZEROS

• Unnecessary computations should be eliminated.

Efficient Code

INITIALIZE PIN-TOTAL
PERFORM VARYING I FROM 1 BY 1 UNTIL I = 40
COMPUTE PIN-TOTAL = PIN-TOTAL + ITEM(I)
END-PERFORM
COMPUTE PIN-TOTAL = PIN-TOTAL * PERCENT DIS

Inefficient Code

INITIALIZE PIN-TOTAL
PERFORM VARYING I FROM 1 BY 1 UNTIL I = 40
COMPUTE PIN-TOTAL = PIN-TOTAL + ITEM (I) * PERCENT DIS
END-PERFORM

• When using PERFORM VARYING clause, using COMP data types is efficient than USAGE DISPLAY for the loop control variables.
• Check boundary always for any arrays. If you expect 100 occurs then always have that check, this helps to know if arrays limit is reached.
• If you need any specific data from file, always load the array with that field instead of complete data from file.