External subsystem command support

IMS provides a command, /SSR, which allows the IMS operator to send commands to the external subsystem.

To receive commands from IMS the external subsystem must supply a Command exit routine. IMS passes the command contained in the /SSR input to this exit routine. AOI (automated operator interface) programs can also send commands to external subsystems using /SSR. The /SSR command input contains identification, a command recognition character (CRC), of the external subsystem to which the command is directed. The CRC for a subsystem is specified as part of the definition of the subsystem to IMS.