IBM OS/390 User Manual

This section discusses some of the compiler option considerations when
converting from the various VSE COBOL compilers to COBOL for OS/390 and
VM.

DOS/VS COBOL has many compiler options that are not available with COBOL
for OS/390 and VM. Compiler options with VS COBOL II or COBOL for VSE/ESA
are generally the same as COBOL for OS/390 and VM. If you are converting VS
COBOL II programs, the most important difference to be aware of is the
RES/NORES option.

One compiler option is provided with VS COBOL II that is not available with
either DOS/VS COBOL or COBOL for OS/390 and VM. This is RES/NORES.

Specifying RES in a VS COBOL II program causes the COBOL run-time
subroutines to be loaded dynamically at run-time. NORES causes the run-time
subroutines to be link-edited with the program.

DOS/VS COBOL behaves in a manner equivalent to specifying NORES with VS
COBOL II. All run-time subroutines are link-edited with the program.

COBOL for OS/390 and VM behaves in a manner equivalent to specifying RES
with VS COBOL II. The run-time is provided by Language Environment, and
run-time subroutines are loaded dynamically at run-time.

In your conversion you should be aware of this different behavior.

Figure 19 on page 261 lists DOS/VS COBOL compiler options that are not
available with COBOL for OS/390 and VM, and gives the COBOL for OS/390 and
VM option you should use instead, if there is one. If you have used any of these
options in your DOS/VS COBOL program, you should remove or change them.

VSE to OS/390 Migration Workbook