P

packet

In data communication, a sequence of binary digits, including data and control signals, that is transmitted and switched as a composite whole. The data, control signals, and, possibly, error control information are arranged in a specific format.

parallel sessions

In CPI-C, two or more concurrent sessions with the same partner LU. See LU-LU session.

partitioned data set (PDS)

A data set in direct access storage that is divided into partitions, called members, each of which can contain a program, part of a program, or data.

partner

An addressable component of a locality; that is, code to which messages can be sent. See also locality.

partner LU

In an APPC or CPI-C conversation, the LU on the far end. The partner LU serves the partner TP. Contrast with local LU. See also partner TP and remote LU.

partner program

For CPI-C, the program receiving the CPI-C call.

partner TP

In an APPC or CPI-C conversation, the TP on the far end. Contrast with local TP. See also partner LU and remote TP.

password

A string of characters that a user, a program, or a computer operator must specify to meet security requirements before gaining access to a system and to the information stored within it.

path

A path exists between two localities when the DMODs in the localities can successfully pass messages between them. A path must exist between two localities before a connection can exist between partners in these localities. See also DMOD and locality.

pattern-matching character

A special character such as an asterisk (*) or a question mark (?) that can be used to represent one or more characters. Any character or set of characters can replace a pattern-matching character. Synonymous with wildcard character.

peer-to-peer

A type of communication in which two systems communicate as equal partners sharing the processing and control of the exchange, as opposed to host-terminal communication in which the host does most of the processing and controls the exchange.

physical unit (PU)

A network-addressable unit that provides the services needed to use and manage a particular device, such as a communications link device. A PU is implemented with a combination of hardware, software, and microcode.

pipe

A portion of memory that can be used by one process to pass information along to another.

protocol

(1) A set of semantic and syntactic rules that determine the behavior of functional units in achieving communication. (2) In Open Systems Interconnection architecture, a set of semantic and syntactic rules that determine the behavior of entities in the same layer in performing communication functions. (3) 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.

PU 2.0

In an SNA network, the component that defines controller and terminal-type resources similar to an IBM 3274 Control Unit.

PU 2.1

In an SNA network, a component such as an intelligent terminal or a PC that works together with LU type 6.2 to support peer-to-peer communications, allowing LUs to function independently from the host.