Implementing User Programs › About the SUBSYS Facility

About the SUBSYS Facility

The SUBSYS facility lets you call user programs and have them run in a separate subtask. This lets you:

• Enhance the &CALL NCL verb by attaching a long-running subtask to handle &CALL requests
• Preserve the state of system resources, such as open files, external database interfaces, and so on
• Reduce the system overheads associated with each call

The SUBSYS facility is supported by the SUBSYS command, and extensions to the &CALL NCL verb.

You should not confuse the subsystems provided by the SUBSYS facility with the z/OS Subsystem Interface, or other z/OS subsystems. These are purely internal subsystems managed by your product.