Envoy Configuration and Management Manual

Subsystem Control Facility (SCF) for Envoy
Envoy Configuration and Management Manual—429861-001
4-5
Object States
The full syntax of each subsystem-specific SCF command for Envoy is given in
Section 5, Subsystem Control Facility (SCF) Commands for Envoy. The syntax of SCF
commands that are not subsystem-specific is given in the SCF Reference Manual for
G-Series Releases.
SCF controls many data-communications subsystems whose individual components are
objects. Each object has an object type and an object name. The object type describes
the type of the object, such as LINE or PROCESS. The object name uniquely identifies
an object within the system.
Object names follow a consistent set of naming conventions. The name of the PROCESS
object, which is created by the START DEVICE command, consists of a dollar sign ($)
followed by a letter and from zero to four alphanumeric characters.
Object States
Objects can have operational states, such as STOPPED, STARTED, or SUSPENDED.
The exact sequence of states an object goes through varies from object to object and
from subsystem to subsystem. Some subsystem commands recognize only a few states.
The operational state of an object at a given instant is important. For example, certain
commands have no effect on objects unless those objects are in a specific state.
For more information on the operational states supported by Envoy, see Envoy Object
States on page 4-7.
Object Attributes
Attributes are the named, configurable characteristics of objects. In SCF for Envoy, you
specify configuration attributes with the ALTER command. For example, you can
change Itbsize, a line attribute, by using the ALTER command.
How SCF Works
SCF performs most commands in the following sequence:
1. When SCF receives a command, it interprets the command and executes it. SCF can
handle some commands without interaction with SCP (for example, OUT).
2. If the command involves control or configuration of a subsystem object or a request
for information about an object, SCF produces a message that describes the object
and the operation. This message passes to an Envoy process through SCP.
3. After the Envoy process has processed the message, it returns a completion message
(one or more messages, if the command is a request for information about an object)
to SCF through SCP. SCF displays the requested information, if any, and then
displays its prompt and waits for the next command. If the completion message
indicates an error condition, SCF displays an appropriate message and then displays
its prompt.