SNAX/APC Management Programming Manual

Glossary
Glossary–8 111813 Tandem Computers Incorporated
resource control block (RCB). A control block that represents the connection of a
transaction program to a half-session.
response unit. In SNA, a message unit that acknowledges a request unit. It may contain
additional information in response to the request.
return code (RC). A value returned at the completion of a command, indicating whether
the command was successful and, if not, the reason for failure.
RH. Request/response header.
RID. Resource ID.
RU. Request/response unit.
SCF. See Subsystem Control Facility.
SCREEN COBOL A procedural language developed by Tandem and based on COBOL
that is used to define and control screen displays on terminals and other input/output
devices. SCREEN COBOL allows programmers to write requester programs that
communicate with operator terminals and intelligent input/output devices, and that
send data to server processes which manage application databases. SCREEN COBOL
programs are compiled into pseudocode form by the SCREEN COBOL compiler and
then interpreted by the TCP (terminal control process).
SDLC. Synchronous data link control.
SDT. Start data traffic request.
secondary logical unit (SLU). One of the two LUs involved in a LU–LU session. The SLU
functions under the control of the remote PLU. It accepts an incoming BIND request
from the PLU.
sense data. In SNA, the data sent with a negative response, indicating the reason for
the response.
service transaction program (STP). A transaction program that provides only a limited
specific network function.
session. In SNA, a temporary logical connection between two network addressable
units for the purpose of exchanging data and control information in accordance with
ground rules that have been agreed upon for that exchange. A session can be
activated, tailored to provide various protocols, and deactivated, as requested.
SLU. See secondary logical unit.
SNA. Systems network architecture.
SNAX/Advanced Peer Networking (SNAX/APN). The Tandem implementation of type 2.1
node operation, in which the Tandem system serves as a low entry networking (LEN)
node.
SNAX/Advanced Program Communications (SNAX/APC). A high-level API that allows
Tandem application programs to communicate with SNA devices and host software
using LU 6.2 conversations. Contrast with SNAX/High-Level Support.