Function Routines/Function Codes

Based on what you want your subsystem to do, you must supply one or more function routines. The same function routine can handle multiple function codes. You must decide how many separate functions you need and identify each function by a unique function code in the subsystem vector table (SSVT). The SSVT identifies:

The SSI function codes to which the subsystem responds
The subsystem routines that process the supported functions.

The MVS-defined function codes your subsystem can support are described in SSI Function Codes Your Subsystem Can Support. If your subsystem handles installation-defined directed requests, you must identify each function using a function code from 236 to 255. These codes are not broadcast functions. You can also subdivide installation-defined function codes by using subtypes you identify by passing parameters in your SSOB function dependent area.

If you plan to have your subsystem support the MVS-defined function codes, see the specific function code descriptions for requirements on your function routine. The sections that follow describe general considerations for all function routines you write.