IBM Z9 Planning Manual page 259

command. (1) A character string from a source
external to a system that represents a request for
system action. (2) A request from a terminal for
performance of an operation or execution of a program.
(3) A value sent on an I/O interface from a channel to a
control unit that specifies the operation to be performed.
configuration. (1) The arrangement of a computer
system or network as defined by the nature, number,
and the chief characteristics of its functional units. More
specifically, the term configuration may refer to a
hardware configuration or a software configuration. (I)
(A) (2) In an ESCON Director, the physical connection
capability determined by a set of attributes. The attribute
values specify the connectivity control status and
identifiers associated with the ESCD and its ports.
console. A logical device used for communication
between the user and the system.
control program. A computer program designed to
schedule and to supervise the execution of programs of
a computer system. (I) (A)
control unit. A hardware unit that controls the reading,
writing, or displaying of data at one or more input/output
units.
controller. A unit that controls input/output operations
for one or more devices.
conversion. (1) In programming languages, the
transformation between values that represent the same
data item but belong to different data types. Information
can be lost through conversion because accuracy of
data representation varies among different data types.
(I) (2) The process of changing from one method of
data processing to another or from one data processing
system to another. (3) The process of changing from
one form of representation to another; for example, to
change from decimal representation to binary
representation.
coupling facility. A special logical partition that
provides high-speed caching, list processing, and
locking functions in a sysplex.
coupling facility channel. A high bandwidth fiber
optic channel that provides the high-speed connectivity
required for data sharing between a coupling facility and
the central processor complexes (or logical partitions)
directly attached to it.
coupling facility control code. The Licensed Internal
Code (LIC) that runs in a coupling facility logical
partition to provide shared storage management
functions for a sysplex.
CP. Central processor.
CPC. Central processor complex.
CPU. Central processing unit.
CS. (1) Central storage. (2) Channel set. (3) Control
storage.
CTC. (1) Channel-to-channel. (2) Mnemonic for an
ESCON channel attached to another ESCON channel.
CUADD. Control unit logical address.
Customer Information Control System (CICS). An
IBM licensed program that enables transactions entered
at remote terminals to be processed concurrently by
user-written application programs. It includes facilities
for building, using, and maintaining data bases.
D
DASD. Direct access storage device.
DCM. Dynamic CHPID Management.
data transfer. (1) The result of the transmission of
data signals from any data source to a data receiver. (2)
The movement, or copying, of data from one location
and the storage of the data at another location.
deactivate logical partition. An operator-initiated
procedure that releases the hardware assigned to a
logical partition, making it available to other partitions.
Contrast with activate logical partition.
Note: The operator should first deactivate the system
control program, if possible or necessary, and
then reactivate the partition, which could provide
a reset to that partition, if required.
deallocate. To release a resource assigned to a task.
Contrast with allocate.
deconfigure. To remove a system resource from the
currently active configuration, usually through the
system control program (SCP) or through the
Configuration (CONFIG) frame on the system console.
default. Pertaining to an attribute, value, or option that
is assumed when none is explicitly specified. (I)
degraded. Pertaining to a mode of operation in which
the system operates with some resources not available.
device. A mechanical, electrical, or electronic
contrivance with a specific purpose.
device address. The 8 rightmost bits of an I/O
address that identify a particular I/O device and a
control unit on the designated channel.
device number. In a channel subsystem, four
hexadecimal digits that uniquely identify an I/O device.
direct access storage device (DASD). A device in
which access time is effectively independent of the
location of the data.
D-3
Glossary