PAM Programming Manual

PAM Programming Manual—142482
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File-System Procedures
Standard file-system procedure calls are used by application processes running in a
Himalaya S-series server to interact with the Port Access Method (PAM) using the
PORT (LLC1 or Ethernet) interfaces. The PORT interface provides link-level access to
the LAN connected to the server.
This section describes file-system procedure calls, such as FILE_OPEN_, READX,
WRITEX, SETMODE, and FILE_CLOSE_, which are used by server-based application
programs to interact with PAM’s programmatic interfaces. These procedures are
described in detail in the Guardian Procedure Calls Reference Manual.
Calling Sequence
Regardless of which one of the supported programming languages is used, the Tandem
NonStop Kernel operating system requires that the following calling sequence be
observed:
1. Open a port
2. Read or Write to a port
3. Close port
File-System Procedure Calls
Application processes running in a Tandem NonStop system use the file-system
procedure calls listed below to interact with PAM.
FILE_OPEN_ Establishes communication between the calling process and
PAM.
FILE_CLOSE_ Terminates communication between the calling process and
PAM.
WRITEX Passes outgoing message data to PAM.
READX Waits for receipt of (and accepts) incoming message data.
SETMODE Allows subsequent nowait I/O operations to complete in any
order with a function code of 30. PAM supports only the
following SETMODE functions:
•
#18 sets the data forward count (DFC) and data forward
time (DFT) parameters
•
#28 (SM^INIT) sets the current DFC and DFT parameters
to the default values defined by an ADD PORT or
ALTER PORT command or to the values set by any
previous SETMODE call SM^THRESHOLD(#18).