IBM OS/390 manual File

features to permit a computing system to execute programs written for another system.

emulator. A combination of programming techniques and special machine features that permits a computing system to execute programs written for a different system. See also integrated emulator, terminal emulator.

entry-sequenced data set. In OS/390 programs with VSAM, a data set whose records are loaded without respect to their contents, and whose relative byte addresses cannot change. Records are retrieved and stored by addressed access, and new records are added at the end of the data set.

error recovery procedures (ERP). Procedures designed to help isolate and, where possible, to recover from errors in equipment. The procedures are often used in conjunction with programs that record information on machine malfunctions.

ESCON. Enterprise Systems Connection - A set of products and services that provides a dynamically connected environment using optical cables as a transmission medium.

ESCON Director. A device that provides connectivity capability and control for attaching any two links to each other.

Ethernet. A 10-megabit baseband local area network that allows multiple stations to access the transmission medium at will without prior coordination, avoids contention by using carrier sense and deference, and resolves contention by using collision detection and transmission. Ethernet uses carrier sense multiple access with collision detection (CSMA/CD).

event control block (ECB). A control block used to represent the status of an event.

exit routine. Either of two types of routines: installation exit routines or user exit routines. Synonymous with exit program.

expiration date. The date at which a file is no longer protected against automatic deletion by the system.

extent. Continuous space on a disk or diskette that is occupied by or reserved for a particular data set, data space, or file.

external side. The receiver of a data entity. A module or routine that accepts a 2- or 4-digit-date format entity for further processing from another module or routine.

F

file.

∙In PSF/MVS, a member of a partitioned data set or a sequential data set

∙In PSF/VSE, a member in a library.sublibrary

file control table (FCT). A table containing the characteristics of files processed by CICS file management.

file name. (1) A name assigned or declared for a file.

(2) The name used by a program to identify a file.

fixed window. A technique to determine the century (high-order digits) of a year when represented by two digits. The 2-digit year is compared against a hardcoded threshold. The century designation is limited to a 100-year range spanning only two centuries. For example, assume the threshold is 60, then if the 2-digit year is ³ 60, the year is in the 20th century; if the 2-digit year is < 60, the year is in the 21st century.

fixed-length record. A record having the same length as all other records with which it is logically or physically associated. Contrast with variable-length record.

foreground partition. In VSE, a space in virtual storage in which programs are executed under control of the system. By default, a foreground partition has a higher processing priority than the background partition.

formatted dump. A dump in which certain data areas are isolated and identified.

forward recovery. (1) The reconstruction of a file by updating an earlier version with data recorded in a journal. (2) The process of reconstructing a file from a particular point by restoring a saved version of the file and then applying changes to that file in the same order in which they were originally made.

G

GDG. See generation data group.

generation data group (GDG). A feature of the MVS catalog that allows a collection of data sets to be kept in chronological order: each data set is called a generation data set.

generation data set. One generation of a generation

data group.

Gregorian calendar. Today′ s general-use calendar of 12 months and 365 days that employs the current leap year algorithm (refer to Leap year below).

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