Availability Guide for Change Management

Tools for Online Change

Availability Guide for Change Management–125506

7-2

How SCF Works

SCF provides an interactive interface to an intermediate process called the Subsystem

Control Point (SCP). SCP interfaces to various I/O processes performing data

communications operations and services. An I/O process pair logically “owns” one or

more I/O devices or communications lines. The devices or lines are physically

connected to the system through a controller; the I/O process pair runs in the pair of

processors to which the controller is attached.

SCP can also be used programmatically. The programmatic interface to SCP is

controlled by the SPI, which builds and retrieves information from command, response,

and event-message buffers.

Figure 7-1 illustrates how SCF relates to the SCP and I/O processes.

Table 7-1. SCF Online Reconfiguration Commands

Command What it does

ADD Adds an object to a communications subsystem.

ALTER Changes the value of one or more attributes of a communications subsystem

object.

DELETE Removes an object from a communications subsystem.

START Starts the operation of an object after it has been added or altered.

STOP Stops the operation of an object. Usually an object must be stopped before it

can be altered or deleted.

Figure 7-1. How SCF Works

Command

File

User Terminal

SCF

SCP

I/O Process

Management

Application

Process