Envoy ACP/XF Configuration and Management Manual

Configuration Quick Start
EnvoyACP/XF Configuration and Management Manual—429232-003
1-7
Reconfiguring Existing Communications Lines
Once the various lines have been characterized, you interact with them by issuing
NonStop OS file-system procedure calls. You first open (activate) each line by calling
the OPEN procedure. Once the line is opened, you use WRITE calls to transmit data
and READ calls to accept incoming data. You can also use other file-system
procedures such as WRITEREAD, CONTROL, SETMODE, DEFINELIST,
CHANGELIST, AWAITIO, and so on. When you have finished using a line, you close
(deactivate) that line by calling the CLOSE procedure. For information about file-
system procedures, refer to the EnvoyACP/XF Application Programming Manual.
When the NonStop OS passes I/O requests to application programs, an EnvoyACP/XF
I/O process acquires the necessary system buffer space, monitors the state of all open
lines for which it is responsible, and returns completion status (and data for read
operations) to the application process.
Figure 1-1 on page 1-8 shows the flow of SCF commands to the EnvoyACP/XF
subsystem. For more information about using SCF to change line attributes, see
Section 4, Subsystem Control Facility (SCF) for EnvoyACP/XF.
Table 1-2. Persistence of Line Attribute Changes
Change Method Persistence
SCF commands to the
WAN subsystem. Changes persist until you change the
DEVICE and/or the PROFILE object in the
WAN subsystem.
SCF commands to the EnvoyACP/XF
subsystem.
Changes persist until you change the
attributes, change the modifiers in the
PROFILE, stop the DEVICE in the WAN
subsystem, or until the system is cold-
loaded.
NonStop OS procedure calls from an
application program to the EnvoyACP/XF
subsystem.
Changes persist only during the application
session.