The IS INITIAL clause on the PROGRAM-ID statement specifies that when a program is called, it and
any programs that it contains will be entered in their initial or first-time called state.
Performance considerations for using IS INITIAL on the PROGRAM-ID statement (measuring CALL overhead only):
One RENT program calling a RENT subprogram 100 times using IS INITIAL on the PROGRAM-ID statement was 1000% to 1500% slower than not using IS INITIAL, depending on the size of WORKING-STORAGE.
Note: These tests measured only the overhead of the CALL (i.e., the subprogram did only a GOBACK); thus, a full application that does more work in the subprogram is not degraded as much.
Using IS RECURSIVE on the PROGRAM-ID Statement.
The IS RECURSIVE clause on the PROGRAM-ID statement specifies that the COBOL program can be recursively called while a previous invocation is still active.
The IS RECURSIVE clause is required for all programs that are compiled with the THREAD compiler option.
Performance considerations for using IS RECURSIVE on the PROGRAM-ID statement (measuring CALL overhead only):
One testcase (Assembler repeatedly calling COBOL) using IS RECURSIVE was 4% slower than not using IS RECURSIVE.
Performance considerations for using IS INITIAL on the PROGRAM-ID statement (measuring CALL overhead only):
One RENT program calling a RENT subprogram 100 times using IS INITIAL on the PROGRAM-ID statement was 1000% to 1500% slower than not using IS INITIAL, depending on the size of WORKING-STORAGE.
Note: These tests measured only the overhead of the CALL (i.e., the subprogram did only a GOBACK); thus, a full application that does more work in the subprogram is not degraded as much.
Using IS RECURSIVE on the PROGRAM-ID Statement.
The IS RECURSIVE clause on the PROGRAM-ID statement specifies that the COBOL program can be recursively called while a previous invocation is still active.
The IS RECURSIVE clause is required for all programs that are compiled with the THREAD compiler option.
Performance considerations for using IS RECURSIVE on the PROGRAM-ID statement (measuring CALL overhead only):
One testcase (Assembler repeatedly calling COBOL) using IS RECURSIVE was 4% slower than not using IS RECURSIVE.
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