A protected subsystem is an application that,
when run, causes the process running the application to be granted
one or more identifiers. For as long as a user runs the subsystem,
the user's process rights list carries these additional identifiers. “How Protected Subsystems Differ from Normal Access Control” shows how
a protected subsystem adds a second level of access control to traditional
controls.
Users with execute access to the application gain
access to the subsystem. Once in the subsystem, users can work with
the data files and other resources of the subsystem.
A subsystem can have several identifiers because
the resources consumed by the subsystem (the files, printers, and
so forth) can be protected differently.
Possession of subsystem identifiers is limited
to the period users are executing the application. Once the users
exit from the application, the identifiers are removed from their
process rights lists. Subsystem identifiers are also removed from
the rights list whenever users enter a Ctrl/Y sequence or attempt
to create a subprocess with the DCL command SPAWN. (In this respect,
use of the subsystem identifiers is identical to the operation of
images installed with privileges.)
The following identifiers
are reserved for use in the security subsystem and should not be granted
to any user:
