System Resource Controller Overview

The System Resource Controller (SRC) provides a set of commands and subroutines to make it easier for the system manager and programmer to create and control subsystems. A subsystem is any program or process or set of programs or processes that is usually capable of operating independently or with a controlling system. A subsystem is designed as a unit to provide a designated function.

The SRC was designed to minimize the need for operator intervention. It provides a mechanism to control subsystem processes using a common command line and the C interface. This mechanism includes the following:

• Consistent user interface for start, stop, and status inquiries
• Logging of the abnormal termination of subsystems
• Notification program called at the abnormal system termination of related processes
• Tracing of a subsystem, a group of subsystems, or a subserver
• Support for control of operations on a remote system
• Refreshing of a subsystem (such as after a configuration data change)

The SRC is useful if you want a common way to start, stop, and collect status information on processes.

Subsystem Components

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: Refer to each specific subsystem for details of its SRC capabilities.

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

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.

SRC Hierarchy

The System Resource Controller has a hierarchical structure (see figure). The hierarchy begins with the operating system followed by a subsystem group (such as tcpip), which contains a subsystem (such as the inetd daemon), which in turn can own several subservers (such as the ftp daemon and the finger command).

List of SRC Administration Commands