Glossary

3270 Data Stream

A protocol for communicating with 3270 display devices.

ACB

Access method Control Block. An area in main storage, used by VSAM and VTAM. In the case of VSAM the ACB is used to describe the data set being accessed, and certain processing options.

bind

The process by which the Database Request Module, produced by the pre-compiler is translated to an application plan.

BLKSIZE

Block Size. The length, in bytes, of a physical record.

BPAM

Basic Partitioned Access Method. An access method for reading members of partitioned data sets.

CAF

Call Attachment Facility. Facilitates access to DB2 from started task and batch address spaces.

clause

A part of an SQL statement.

column

In a DB2 table, a specific type of data that is named and whose values are contained in zero or more rows.

commit

A DB2 operation that terminates a unit of work and makes any changes that have been made permanent.

control area

(CA) A grouping of control intervals, used by VSAM for managing the space allocated to a VSAM data set.

control interval

(CI) a grouping of records. The minimum number of records transmitted between main storage and auxiliary storage in a single operation.

cursor

A DB2 control structure used to retrieve rows from a result set.

DCB

Data Control Block. This control block contains information pertaining to the structure of records and blocks a file.

ddname

Data Definition name. The name associated with a data set by a JCL DD statement or the TSO allocate command.

dequeue

Relinquishing a reservation for a system resource.

direct access

In VSAM, the accessing of individual records directly. Using direct access, the records preceding the record you want are not read (or written).

DFP

Data Facility Products. A group of IBM supplied access methods and utilities.

DFSMS

Data Facility System Managed Storage. A group of IBM- supplied access methods and utilities. DFSMS supercedes DFP.

DFSORT

A DFP program for sorting data sets into user specified order.

enqueue

A reservation for a system resource.

ESDS

Entry-sequenced Data Set. One of the data set organizations supported by VSAM. The data is organized by the order it is entered.

EXEC

(1) a TSO command for running REXX programs. (2) A REXX program.

full-screen mode

A method for displaying information on a terminal where the unit of display is the entire display surface.

function

A subprogram called by a REXX exec that returns a value. A function call in an expression can be thought of as being replaced by its value.

host variable

A DB2 term for a program variable in an application program. Host variables are used in SQL commands.

KSDS

Key-sequenced Data Set. One of the data set organizations supported by VSAM. The data is organized by the collating sequence of the key field.

LDS

Linear Data Set. One of the VSAM data set organizations. Supports the MVS Data-In-Virtual (DIV) facility.

line-mode

A way of presenting information on a terminal where the unit of display is a single line.

LRECL

Logical Record Length.

orders

Hexadecimal codes in 3270 data streams which direct the control unit's actions.

packed decimal

A binary-encoded format for decimal numbers in the 360/370/390 hardware architectures. Each decimal digit occupies a half byte (nibble). The sign of the number is in the right-most nibble.

PDS

Partitioned Data Set. A data set organization for holding collections of related records in groups called "members".

PDSE

Partitioned Data Set Extended. The PDSE is identical to the PDS organization, but has additional sharing and space managment capabilities.

predicate

In SQL, a comparison operation that is used in a query.

QSAM

Queued Sequential Access Method. A file access method for reading, writing and updating sequential data sets and partitioned data set members.

REXX

Restructured EXtended eXecutor. A programming language for SAA environments.

rollback

A DB2 operation that terminates a unit of work and backs out all changes that have been made.

row

In a DB2 table, a sequence of values, one for each column in the table.

RPL

Request Parameter List. An area in main storage which describes a request for services to VSAM.

RRDS

Relative Record Data Set. One of the organizations supported by VSAM. The data is organized by record number.

SAA

Systems Application Architecture. A set of software interfaces for building portable applications.

SAF

System Authorization Facility. An MVS facility for routing authorization requests to RACF or equivalent system security packages.

SQL

Structured Query Language. The collection of commands used to create, modify, query, and delete DB2 objects.

stem

(1) A type of REXX program variable that permits the construction of pseudo-array data structures; (2) the part of a stem variable that lies to the left of the first dot (.). The simple symbol which makes up the stem is never replaced by its value.

table

A DB2 object that contains data in row/column format.

thread

A DB2 structure that describes the connection between an MVS task and the DB2 address space.

TTR

Track Track Record. An address (3 bytes in length) that describes a location within a file relative to the beginning of the file. The distance is given in tracks and records.

unit of work

In DB2, a recoverable sequence of commands within an application.

virtual storage

An operating system technique for providing more addressable storage to programs than is actually available on the hardware.

VSAM

Virtual Storage Access Method. VSAM data sets may be accessed sequentially and randomly.

VRDS

Variable Length Relative Record Data set.

Wild Card

A character in a pattern that may match against any character in a target string. Some wild card characters may match against many target string characters.