HP OpenVMS Systems Documentation

HP COBOL
DBMS Database Programming Manual

DB-CURRENT-RECORD-NAME: A database special register containing the name of the record type of the current record of the run unit. It contains spaces if there is no current record of the run unit.

DBA: See database administrator.

DBCS: See Database Control System.

dbkey: See database key.

DB-KEY: A database special register that holds the dbkey of the record accessed by the last FETCH, STORE, or FIND statement. This special register can be used to fine tune storage strategies in the database.

DBMS: See database management system.

DBQ: See Database Query Utility.

DB-UWA: A database special register which serves as the record delivery area that the Database Control System (DBCS) uses to make data items available to your program.

DDL: See data definition languages.

de-edit: The logical removal of all editing characters from a numeric edited data item in order to determine that item's unedited numeric value.

deadlock: A database processing situation in which two or more run units are stopped by conflicting requests for locked records.

DML: See data manipulation language.

DMU: See Dictionary Management Utility.

empty set: A database set occurrence containing no member records.

EXCLUSIVE usage mode: The state of a realm in which it cannot be accessed by a concurrent run unit.

FIXED member: A record, upon becoming a member of a set occurrence of a FIXED set type, that must remain a member of that set until it is erased from the database. Fixed set membership is declared in the schema DDL. Compare with MANDATORY member.

INSERTION class: An attribute of member records that describes how and when members are added to database sets. See also AUTOMATIC member and MANUAL member.

journal file: A database file that contains all records modified by a run unit, usually chronologically ordered. A journal file allows reconstruction of the data to prefailure conditions in case of database contamination due to system or program failures.

journaling: The act of creating, writing, or both, to a journal file.

junction record: A record inserted between two records of the same type. You can use a junction record to simulate what would otherwise be an illegal set relationship for Oracle CODASYL DBMS, that is, a record type being a member of a set that it owns. Also, using a junction record helps avoid data redundancy and inconsistency.

keeplist: A list of database keys used by a run unit to lock records for later reference.

locking: HP COBOL has facilities that allow concurrent use of a database or a sequential, relative, or indexed file without corrupting their records. RMS on OpenVMS VAX maintains locks on a file, whereas RMS on OpenVMS Alpha maintains locks on files and records. In Oracle CODASYL DBMS, locks are maintained on individual records, entire realms, or both.

MANDATORY member: A record, upon becoming a member of a set occurrence of a set type, must remain a member of that or some other set occurrence of that set type until it is erased from the database. MANDATORY set membership is declared in the schema. Compare with FIXED member.

MANUAL member: A database record that becomes a member of a given set by explicit direction of the application program using the CONNECT statement. MANUAL set membership is declared in the schema.

member condition: The condition, for which a truth value can be determined, that a database record is a member of one or more sets.

member record: A database record, other than the owner record, included in the set. There may be one or more member record types in a set. There may be zero or more member records in a set.

nonsingular set: A database set not owned by the SYSTEM. See also SYSTEM-owned set and owner record.

null: A data attribute associated with currency indicators and database key values. This attribute is independent of the value of the contents of data items.

OPTIONAL member: A database record that does not necessarily remain a permanent member of a set. Its membership in a set may be changed using the DISCONNECT statement without its being deleted from the database. OPTIONAL set membership is declared in the schema.

Oracle CDD/Repository: The central repository of information about data elements, data structures, and relationships between data structures. Oracle CDD/Repository is used by Oracle CODASYL DBMS, Datatrieve, and HP COBOL. It does not contain actual data files. Rather, it contains definitions of schemas, storage schemas, and subschemas. Oracle CDD/Repository is available under a separate license.

owner record: The head of a group of database records that make up a set. There can be only one record type as the owner for each set type and one owner record occurrence for each set occurrence.

PROTECTED usage mode: The state of a realm in which it may be retrieved from but cannot be modified by concurrent run units.

quiet point: A time when no run units are accessing a database. Quiet points and transactions are mutually exclusive (for the entire database). Compare with transaction.

For the run unit, the time between a COMMIT or ROLLBACK, and the following READY.

ready mode: The state of a realm after execution of a READY statement for that realm and before the execution of a COMMIT or ROLLBACK statement for that realm.

realm: One or more schema areas. Realms are declared in the subschema. See also area.

realm currency indicator: A currency indicator (in other words, database key value) associated with a particular realm. A realm currency indicator identifies a particular database record, position in the realm, or both.

record key: A key whose contents identify a record in an indexed file or within a record type in a database. Within an indexed file, record key is either the prime record key or an alternate record key. Within a database, a record key may or may not have ordering significance.

record occurrence: A user-stored instance of a record type. A record occurrence is the actual physical data representation of a single record in the database, but not its definition, which is the record type.

record order key: A record key associated with a record type in a database. The definition of a record order key in the schema causes the DBCS to maintain the records in the specified logical sequence based on values of the record order key.

record selection expression: A word or group of contiguous words in a COBOL source program that specifies the algorithm to be used by the Database Control System (DBCS) to identify a specific database record.

record type currency indicator: A currency indicator associated with a particular database record type. A record type currency indicator identifies a particular record of the record type. If the subschema includes a record order key for a record type, its associated currency indicator identifies a particular record, position in the record type, or both.

RETRIEVAL usage mode: The state of a realm in which the current run-unit may only retrieve from it.

schema: The logical description of a database, including data definitions and data relationships. The schema is written using the schema data definition language (schema DDL).

schema DDL: The language used to define the logical structure of a database.

schema-name: A user-defined word that identifies a schema.

section header: A combination of words (followed by a separator period) that indicates the beginning of a section in the Environment, Data, and Procedure Divisions of a COBOL program. In the Environment and Data Divisions, a section header consists of reserved words followed by a separator period in the Division. SUB-SCHEMA SECTION is a valid section header.

set: A defined relationship among records in a database. A set contains an owner record and zero or more member records. See also set occurrence , set type, and empty set.

set member: A record stored in the database as a nonowner participant in a specific set.

set-name: A user-defined word that identifies a set type.

set occurrence: An instance of a database set type. A set occurrence is the actual data in the set, not its definition, which is the set type.

set-ordering criteria: The specification for the positioning of a member record in a set by the DBCS. The schema defines this specification.

set owner: A database record occurrence whose existence establishes the existence of a specific set occurrence.

set type: A specific named set that has been defined in the schema data definition language. It is the definition of a collection of sets that have identical characteristics. Set types are declared by the schema data definition language.

set type currency indicator: A currency indicator associated with a particular database set type. A set type currency indicator identifies a particular set of the set type and a particular record, position in that set, or both.

simple condition: Any single condition from the following list:

relation condition
class condition
condition-name condition
switch-status condition
sign condition
success/failure condition
simple-condition (in parentheses)
tenancy condition (Oracle CODASYL DBMS simple condition type)
empty condition (Oracle CODASYL DBMS simple condition type)
database key condition (Oracle CODASYL DBMS simple condition type)

singular set: See SYSTEM-owned set.

storage schema: A description of the physical storage of data in database files. The storage schema is written using the storage schema data definition language.