Subsystem components

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The following are the properties and components of a subsystem.

A subsystem can have one or more of the following properties:

  • Is known to the system by name
  • Requires a more complex execution environment than a subroutine or nonprivileged program
  • Includes application programs and libraries as well as subsystem code
  • Controls resources that can be started and stopped by name
  • Requires notification if a related process is unsuccessful to perform cleanup or to recover resources
  • Requires more operational control than a simple daemon process
  • Needs to be controlled by a remote operator
  • Implements subservers to manage specific resources
  • Does not put itself in the background.

A few subsystem examples are ypserv, ntsd, qdaemon, inetd, syslogd, and sendmail.

Note: See each specific subsystem for details of its SRC capabilities.

Use the lssrc -a command to list active and inactive subsystems on your system.

The following defines subsystem groups and subservers:

Subsystem Group

A subsystem group is a group of any specified subsystems. Grouping subsystems together allows the control of several subsystems at one time. A few subsystem group examples are TCP/IP, SNA Services, Network Information System (NIS), and Network File Systems (NFS).

Subserver

A subserver is a program or process that belongs to a subsystem. A subsystem can have multiple subservers and is responsible for starting, stopping, and providing status of subservers. Subservers can be defined only for a subsystem with a communication type of IPC message queues and sockets. Subsystems using signal communications do not support subservers.

Subservers are started when their parent subsystems are started. If you try to start a subserver and its parent subsystem is not active, the startsrc command starts the subsystem as well.