DSSM acts as the central mechanism responsible for managing the interrelations between the subsystems, allowing various relations to be explicitly monitored.
Job relations to a subsystem via explicit or implicit connections are set up and monitored by DSSM. A job relation can always be established between a task and a job entry.
Address relations via linkage editors and loaders must be specified explicitly in an operand of the SSCM statement SET-SUBSYSTEM-ATTRIBUTES (REFERENCED-SUBSYSTEMS). However, the operand should only be applied to subsystems from the same “family” (privilege level, memory class, etc.). In the case of unbundled subsystems, system administration should only select dynamic addressing mechanisms (SVC, ISL or system exit mechanisms for privileged subsystems; the BLS interface, BIND, for nonprivileged subsystems).
Address relations restrict the unloadability of a subsystem, since unloading has to take place in the reverse order from loading. Address relations are taken into account during loading and unloading, but they are not monitored. They prevent a subsystem from being unloaded, regardless of whether or not jobs exist.
Dependency relations require the availability of another subsystem. These relations can be declared by means of the RELATED-SUBSYSTEMS operand of the SSCM statement SET-SUBSYSTEM-ATTRIBUTES and are taken into account in the loading and unloading sequences.