The slide currendy in the work area during design mode.
Cursor:
_ A highlighted area that indicates your place on the screen. In DECslide, the cursor for graphics objects is diamond shaped. The text cursor is rectangular.
Data Definition Language Utility (CDDL):
The VAX CDD utility that lets you insert record definitions into the CDD. You create the datil descriptions in a CDDL source file, and you compile the source filewith the CDDL compiler.
Data Definition Languages (DDL):
In VAX DBMS, the languages used to describe schemas, subschemas, and storage schemas.
In VAX RdbIVMS, a set of statements that allow you to define the structure and characteristics of stored data. You use data definition language to describe fields, relations, views, indexes, and constraints. The RdblVMS data definition language is part of ROO, the interactive RdblVMS utility.
See also schema data definition entry, storage schema data definition entry, and subschema data definition entry.
Data Entry Phase:
The stage in which you provide data to DECgraph through the Keyboard Data Entry Screen, a load file, or VAX DATATRIEVE. The DATA icon leads to a sub-menu of icons representing the three methods for entering data.
Data File:
A DECgraph file that contains the actual data for a chart, including
the
X and y values. Data files have the file type _.GRD.Data Item:
<i'. In DBMS, the smallest unit of named data in a record type. A data item can be a single value or an array of one or more values.
• In RdbIVMS, the smallest unit of data. A data item occupies a single field in a record.
Data Item Occurrence:
In DBMS, one occurrence of a data item type.
See also data item type and record occurrence.
Data Item Type:
In DBMS, the smallest unit of defined data. A data item type can represent a single value or an array of one or more values.
- - - - Seealsooata
Item occurrence and record type.G-15 Data Manipulation Facility:
The part of DATATRIEVE that parses, optimizes, and executes all commands and statements passed to DATATRIEVE.
Data Manipulation Language (DML):
In DBMS, the statements that pertnit programs written in VAX languages to access the database.
In RdbIVMS, A set of statements that allow you to store, retrieve, modify, and erase data from a database. RdblVMS provides two methods of manipulating data:
• Embed the data manipulation statements in a high-level language such as COBOL.
• Issue the data manipulation statements directly, using the ROO utility.
DataSet:
One file that includes both the identification and data files, all the basic infor-mation needed to produce a chart.
See also data file, identification file.
Data Type:
A characteristic assigned to a field that determines the kind of data the field can contain.
In TDMS, you determine the data type of a form field in the field identifiers and field validators of the form definition. You determine the data type of a record field in the data type statement of a record definition.
Data Value:
A user-assigned value of a data item occurrence.
See also data item occurrence and data item type.
Database:
A collection of interrelated data on one or more mass storage devices. The col-lection is organized to facilitate efficient and accurate inquiry and update.
In a database, more than one user can access the data at the same time. Data integrity and security are provided by the database.
See also relational database.
Database Adminisrrator (DBA):
The person or group of people responsible for planning, designing, implement-ing, and maintaining a database.
G-16 • Glossary
Database Control System (DBCS): . ..
The DBMS or RdbNMS component that, together with theVAXlVMS operating system, provides run-time control of database processing ..
Database Key (dbkey): " ..
In DBMS and RdbNMS, a unique value that identifies. a record in a database.
The Database Control System assigns the value when a record is stored in the database.
In DBMS,your run unit cannot directly access database
keys,
but they are used by the Database Control System whenever you store, retrieve, or manipulate a record.In RdbNMS, your program can retrieve the database key and use it to access a record.
Database Management System:
A system for creating, maintaining, and accessing a collection of interrelated data records that may be processed by one or more applications without regard to physical storage. Data is described iridependendy of application programs;
providing ease in application development, data security; and data visibility.
The VAX Information Architecture includes tWo database management systems:
• VAX DBMS, a DIGITAL software product that complies with the standards for database management systems established by CODASYL
•. RdbNMS, a database management system based on the relational data model See also database, RdbNMS, and relational database.
Database Pages:
The structures used to store and locate data in a DBMS or RdbNMS database.
Database pages consist of one or more disk blocks of 512 bytes each.
DBMS uses page-clustered I/O, a technique that retrieves groups of physically-related database pages, rather than an individual page, in response to a run unit's request for data.
Database Query (DBQ):
In DBMS, a data manipulation utility that interprets data manipulation state- . ments. DBQ provides access to data through both interactive and callable modes. Interactive DBQ is a DBMS query language. Callable DBQ provides access to the database for programs written in high-level languages.
See also Callable DBQ and Interactive DBQ.
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DATATRIEVE:
A VAX data management language for manipulating, storing, and modifying records from RMS data files, DBMS databases, and RdblVMS databases. DATA-TRIEVE is callable from a variety of high-level languages.
DATATRIEVE Procedure:
See procedure.
DBA:
See database administrator.
DBCS:
See Database Control System.
Dbkey:
See database key.
DBMS:
Used commonly, DBMS can refer to any database management system. In VAX Information Architecture documentation, DBMS usually refers to VAX DBMS, a DIGITAL software product that complies with the standards for database man-agement systems established by CODASYL.
See also database management system.
DBQ:
See database query and Callable DBQ.
DBR:
In DBMS, the name of the process that performs database recovety. It is called by the Monitor at restart.
OCL:
DIGITAL Command Language.
OCL Command Procedure:
A sequence of DIGITAL Command Language (DCL) commands stored in a file;
sometimes referred to as a DCL procedure.
DCLServer:
One of two types of servers used to handle processing work for ACMS tasks. A DCL server handles images, DATATRIEVE commands, and DCL commands and command procedures.
See also server, DCL server image, and procedure server.
DCL Server Image:
The image, provided by ACMS, that is loaded into a DCL server process when the process is started by the application execution controller. The DCL server images allows you to use images, DATATRIEVE commands, and DCL com-mands and procedures to implement processing for tasks.
See also procedure server image.
G-18 • Glossary
DCL Server Process:
See server process.
DDL:
See data definition languages.
Deadlock:
A situation in which two or more processes request the same set of resources and there is no method for resolving the conflict. For example, if process A has record 1 locked and requests record 2 while process B has record 2 locked and is requesting record 1, a deadlock occurs between processes A and B.
VAX DBMS resolves all deadlock situations.
Deadly Embrace:
See deadlock.
DECnet:
The DIGITAL software facility that enables a user to access information on a remote computer via telecommunications lines. DECnet/VAX enables a VAX/VMS operating system to function as a network node.
Default:
A value that is assumed unless - or until - you specifically indicate another choice. For example, Palette 1 is the default palette for DEC slide and DECgraph.
Default Dictionary Directory:
The CDD directory assigned to you when you invoke an image that uses the CDD. This directory becomes the starting directory for path names. You can define a directory as the default by assigning a path name to the VAX!VMS logi-cal name CDD$DEFAULT. If you do not, the default directory is CDD$TOP. The CDD Dictionary Management Utility and some command qualifiers allow you to set temporary default directories. You can also set the default directory with the DATATRIEVE SET DICTIONARY command.
Default Directory:
In DECslide, the storage area used to locate the files where you are creating your slide designs. You always save your slides in your default directory.
See also slide directory.
Default Slide:
A slide DECslide identifies with the name CURRENT that you can use instead of specifying a slide name in answer to a file option prompt. You can change this name for a DECslide session when you specify the input and output parameters in the command string.
G-J9
Degree (of a relation):
The number of fields in a relation definition_