An acronym for the Conference on Data Systems Languages, the committee that designed the COBOL language and provided the guidelines used in the development of VAX. DBMS.
CODASYL-compliant:
Any database system that conforms to the guidelines set by the Conference on Data Systetns Languages.
Collating Sequence:
The sequence in which characters are ordered for sorting, merging, and comparing.
Collection:
• In VAX. DATATRIEVE, a type of record stream formed with the FIND state-ment. You can name a collection in order to have several collections available at once.
• In DBMS, all occurrences of records that belong to a specific record type. / . . _Record.~~!i.m_dJ:fuLedID.!icll~m.all!1.ds!lQs~~t~. __________ _ See also CURRENT.
G-II
Column:
A set of numbers or words arranged vertically. For example, the DECgraph Keyboard Data Entry Screen has a column of Y legend values ranging from Y 1 (bottom) to Y6 (top).
See also field.
Column Headers:
The heading that labels the columns of data in a DATATRIEVE report or in the output of a DATATRIEVE PRINT statement.
Command:
An
instruction, generally an English word, typed by the user at a terminal or included in a command procedure that requests the software monitoring a ter-minal or reading a command procedure to perform some predefined operation.In DATATRIEVE, a command is distinct from a statement. DATATRIEVE com-mands usually deal with the Common Data Dictionary and perform data description functions. DATATRIEVE commands cannot be combined with each other and cannot be used in statements.
See also statement.
Command Line:
See command string.
Command Process:
The process in the ACMS terminal control subsystem that handles user login and interaction between terminals and ACMS.
Command String:
A line (or set of continued lines) consisting of a command and, optionally, infor-mation modifYing the command, including its qualifiers and parameters. For example, in DECslide, the SLIDE command string uses the following format:
SLIDE[!qualifiers] [slidcname] [new_slidcname]
In DECslide and DECgraph, you can use the command string for either an inter-active or noninterinter-active session.
See also interactive mode, non interactive mode.
Comment Character:
In DECgraph, either a C, an asterisk, or exclamation point used to indicate a comment in the load file. Comments let you document the contents of your load file; they do not appear as data. For example:
C The data type for X values is TEXT.
lLDAT.L1YPE TEXT
G·12 • Glossary
COMMIT:
• In DBMS, a function that terminates a recovery unit and makes permanent all database updates initiated by the recovery unit.
• In ACMS, also an Application Definition Utility keyword used when defining tasks with recovery.
• In Rdb/VMS, a statement that completes a transaction by entering the changes in the physical database @e.
See also RETAINING and rollback.
Common Data Dictionary (CDD):
A central storage facility consisting of a hierarchy of directories that contain definitions used by VAX Information Architecture products. The CDD contains descriptions of data, not the data itself. CDD objects are stored hierarchically and are accessed by reference to dictionary path names.
CDD directories and subdictionaries contain objects such as:
• ACMS application, menu, and task group definitions
• DATATRIEVE domain, record, and procedure definitions
• DBMS schema, subschema, and storage schema definitions
• TDMS record and form definitions, requests, and request library definitions
• Rdb/VMS database, relation, field, index, and constraint definitions Compound Object:
An
object formed by using the JOIN key to combine more than one graphics object, text object, or both.COMPUTED BY Fidds:
Virtual fields that appear in a DATATRIEVE record definition or an RdblVMS relation or view definition, but not in the physical record. Because the value of a COMPUTED BY field is computed as part of a statement, it occupies no space in the record.
Concurrency:
The simultaneous use of a database by more than one user.
Conditional Expression:
A string of symbols that can be evaluated as true or false. For example, in the statement FOR E IN EMPLOYEES WITH E.STATE = "MA", the conditional expression is E.STATE = "MA". Also called Boolean expression.
__ See.also
Boolean expressiouc_G·]3
Conditional Instruction:
A TDMS request instruction that executes only if certain conditions are true.
TDMS executes a conditional instruction if the value in a control field matches the case value specified within the conditional instruction.
Conditional Request:
A request containing one or more conditional instructions.
See also conditional instruction.
Constraint:
A set of criteria that restricts the values in a field. In Rdb/VMS, you set up con-straints using the DEFINE CONSTRAINT statement.
Context Variable:
A temporary name that identifies a record stream to RdbIVMS.
Once you have associated a context variable with a relation, you use only that context variable to refer to records from that relation in the record stream or loop you created. In this example, E is a context variable:
FOR E IN EMPLOYEES PRINT E. END_FOR
You can also use context variables in DATATRIEVE to resolve context ambiguity.
Control Field:
A program record field, also specified in a TDMS request, whose value deter.
mines whether or not TDMS executes a conditional instruction.
See also conditional instruction.
COPY Field Description Statement:
A CDDL statement that inserts the field descriptions of existing records into the descriptions of new records.
Cross Operation:
See join operation.
Cross Product:
A relation that is the result of performing a join operation to combine every row in one relation with every row in another.
Currency Indicators:
DBMS pointers that serve as place markers in the database for the Database Control System (DBCS) and your run unit.
CURRENT:
• In DBMS, identifies which database records or positions are being used as currency indicators.
• In DATATRIEVE, identifies the most recently formed collection.
G-14 • Glossary