Technical data

This file name may vary depending on the version of DBMS you are using.
For example, if you are using DBMS Version 7.2, the command would be the
following:
$ LINK DMLPROG,SYS$LIBRARY:DBMDML72/OPT
1.6 Running an HP COBOL DML Program
You use the DCL command RUN to execute your HP COBOL DML program.
At run time, the Database Control System (DBCS) fills a variety of roles in
HP COBOL. Its major functions are to monitor database usage, act as an
intermediary between HP COBOL and the OpenVMS operating system, and
manipulate database records on behalf of user programs. Upon execution of the
first DML statement, the DBCS implicitly executes a BIND statement that links
the run unit to the database. If the BIND statement is unsuccessful, a database
exception occurs.
The DBCS also enforces the subschema view of the database. For example, a
database schema record may contain 20 data items. However, a subschema
record may only define 10 of those data items. If a FETCH statement references
this record, the DBCS only retrieves those defined 10 data items and makes
them available to the COBOL program in the user work area (UWA). The other
10 items are not available to the COBOL program. Figure 1–2 illustrates the
run-time relationships between an application program requesting subschema
data (a FETCH statement, for example), the DBCS, and the data the subschema
describes.
Figure 1–2 Database and Application Program Relationship
COBOL
Application
Program
(FETCH)
ZK-1478-AI
Database
Control System
(DBCS)
Subschema
Data
1–6 Program Organization and Structure