SNAX/APC Configuration and Management Manual

Introduction to SCF for SNAX/APC
SNAX/APC Configuration and Management Manual—138787
6-7
How SCF Works
For more information about the operational states supported by SNAX/APC, see Object
States in Section 7, Objects for SNAX/APC.
How SCF Works
For commands that relate only to the SCF session (such as VOLUME), SCF takes the
appropriate action without communicating with SCP. For commands that relate to a
subsystem or its objects, SCF translates the command into a formatted message for SCP,
which then communicates with the appropriate subsystem to perform the specified task.
SCF accepts commands from a terminal, a disk file, or an application process. It sends
display output to a terminal, a file, a process, or a printer. When SCF is started
interactively, the input source and output destination are specified in the TACL RUN
command used to start SCF. If SCF is started by a operating system process-creation
procedure, its input source and output destination are taken from the startup message.
Subsequent SCF commands can change the input source and output destination.
SCF resides in a file called $SYSTEM.SYSTEM.SCF. In addition to using the TACL
RUN command to start SCF interactively, you can start SCF by using a command
(Obey) file, a TACL macro, or a TACL routine.
Input Sources
SCF accepts command input from a terminal or a disk file. The initial input source is
determined by the form of the RUN command used to initiate SCF. At any time during
an SCF session, the input source can be temporarily changed to execute a sequence of
commands from a command (Obey) file.
Modes of Operation
SCF can be run in two modes: interactive or noninteractive. Because interactive and
noninteractive input are treated quite differently by SCF, the following distinctions are
important:
•
The mode is interactive when both input and output pass through the same terminal,
or when the same process is used for both input and output. Conversely, using the
OUT command or the / OUT file-spec / parameter within a command line, to
direct output to a location different from that of the input, causes SCF to run in the
noninteractive mode.
This rule affects the use of abbreviations when you enter keywords. Abbreviations
formed by truncating keywords, provided that the result is unambiguous, are
permitted in the interactive mode but not the noninteractive mode. For example, in
the interactive mode, you can abbreviate the VERSION command to VE; in the
noninteractive mode, you must spell out VERSION.
•
Interactive input from a terminal is characterized by the entry of a command and any
parameters it might include, followed by a carriage return. When a process is used
for both input and output, SCF waits for the process to send a request and treats the
process in the same manner as a terminal.