Compiling and linking COBOL programs for running under IMS

For best performance in the IMS environment, use the RENT compiler option. RENT causes COBOL to generate reentrant code. You can then run your application programs in either preloaded mode (the programs are always resident in storage) or nonpreload mode without having to recompile using different options.

Preloading can boost performance because subsequent requests for a program can be handled faster when the program is already in storage (rather than being fetched from a library each time it is needed).

For IMS programs, using the RENT compiler option is recommended. You must use the RENT compiler option for a program that is to be run preloaded or both preloaded and nonpreloaded. When you preload a program object that contains COBOL programs, all of the COBOL programs in that program object must be compiled using the RENT option.

You can place programs compiled with the RENT option in the z/OS® link pack area. There they can be shared among the IMS dependent regions.

To run above the 16 MB line, an application program must be compiled with RENT. The data for IMS application programs can reside above the 16 MB line, and you can use DATA(31) RENT for programs that use IMS services.

For proper execution of COBOL programs under IMS, observe the following guidelines for the link-edit attributes:
  • To link program objects that contain only COBOL programs compiled with the RENT compiler option, link as RENT.
  • To link program objects that contain a mixture of COBOL RENT programs and other programs, use the link-edit attributes recommended for the other programs.

Related concepts  
Storage and its addressability

Related tasks  
Choosing the DYNAM or NODYNAM compiler option  
Language Environment® Programming Guide (Condition handling under IMS)

Related references  
Enterprise COBOL for z/OS Migration Guide (IMS considerations)