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detection in the field, a card read-in operation, or
program control. The modified data tag may be reset
by a selector-pen detection in the field, program control,
or ERASE INPUT key.
Modify Field (MF). An order that allows specified field
attributes to be modified.
Network Logical Data Manager (NLDM). An IBM
program product that collects and correlates LU-LU
session-related data and provides the user with online
access to the data.
It
runs as a Network
Communications Control Facility (NCCF)
communication network management application
program.
Network Problem Determination Application (NPDA).
An IBM program product that helps the user identify
network problems from a central control point using
interactive display techniques.
Network Terminal Option (NTO). An IBM program
product that extends the capabilities of the ACF/NCP
to support a select group of non-SNA devices.
nonswitched line. A telecommunication line on which
connections do not have to be established by dialing.
Contrast with switched line.
null modem. A type of modem eliminator that wraps
signals but does not provide redrive or clocking of
signals. A passive, device used to connect two DTEs
together for communication purposes. A null modem
typically provides cross-over only for the required
signals (such as, Transmit Data and Receive Data) with
no redrive. A null modem replaces a pair of modems
on a phone line. Null modems do not provide clocking.
order code. A code that may be included in the write
data stream transmitted for a display station or printer;
provides additional formatting or definition of the write
data.
order sequence. A sequence in the data stream that
starts with an order code and includes a character
address and/or data characters related to the order code.
outbound. Transmissions from the host to the 3708.
outgoing group. In systems with TCAM, that section of
a message handler that manipulates outgoing messages
after they have be.en removed from their destination
queues.
pacing. (1) A technique by which a receiving station
controls the rate of transmission of a sending station to
prevent overrun. (2) In SNA, a technique by which a
receiving component controls the rate of transmission of
a sending component to prevent overrun or congestion.
physical unit (PU). In SNA, the component that
manages
an~
monitors the resources (such as attached
links and adjacent link stations) of a node, as requested
by an SSCP via an SSCP-SSCP session.
platen. (TC9S) The part of a document copying
machine, usually in the form of a glass plate that can be
curved, upon which the original is placed for copying.
A backing, usually cylindrical, against which printing
mechanisms strike or otherwise deposit ink to produce
an image.
point-to-point connection. A connection established
between two data stations for data transmission. The
connection may include switching facilities.
polling. A technique by which each of the terminals
sharing a communication line is periodically
interrogated to determine whether it requires servicing.
primary logical unit (PLU). In SNA, the logical unit
(L U) that contains the primary half-session for a
particular LU-LU session. Contrast with secondary
logical unit.
printer authorization matrix. A matrix stored in the
3274 control unit that establishes printer assignment and
classification.
program attention key. On a display device keyboard, a
key that produces an interruption to solicit program
action.
program function key. (1) (TC9S) On a typewriter, a
control by means of which a specified machine function
is set, released or performed. (2) (TC97) In computer
graphics, a button or switch that may be operated to
send a signal to the computer program controlling the
display. (3) On a terminal, a key, such as an
ATTENTION or an ENTER key, that causes the
transmission of a signal not associated with a printable
or displayable character. Detection of the signal usually
causes the system to perform some predefined function
for the operator.
.
Program Tab
(PT)
order. An order that advances the
current buffer address to the address of the first
character location of the next unprotected field.
protected field. A display field for which the display
operator cannot use the keyboard or operator
identification card reader to enter, modify, or erase
data.
protocol. (1) (CCITT/ITU) A specification for the
format and relative timing of information exchanged
between communicating parties. (2) In SNA, the
meanings of, and the sequencing rules for, requests and
responses used for managing the network, transferring
data, and synchronizing the states of network
components.
protocol conversion. For the 3708, the changing of
start-stop data sent from an ASCII device to an SNA
Glossary
X-9
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