Database and Expert System Technology - Information Systems Reengineering, Integration and Normalization - page 33

Path 1 Path 2 Path 3 Path 4 Path 5
Loan Cont Loan Cont. Loan Cont. Loan Cont. Loan Cont.
Loan Drawdown Loan Interest Loan Interest Loan Repayment Loan balance
Fixed Rate Indexed Rate
The commands in any Data Manipulation Language (DML), can be divided into
two sets, retrieval and modification commands. The following are the syntax of the
hierarchical DML of IMS (IBM's Information Management System, a hierarchical
DBMS). There are four parameters in IMS DML. They are:
• FunctionCode, which defines the database access function
• ProgramControlBlock, which defines the external subschema access path
• I-O-Area, which is a target segment address
• SegmentSearchArgument,whichdefinesthetargetsegmentselectioncriteriaas
follows:
CALL “ CBLTDLI ” USING FUNCTION-CODE
Note: CBLTDLI is a call by a COBOL program to access the DL/1 database.
Retrieval Command:
• GetUnique(GU)
This command retrieves the leftmost segment that satisfies the specified condi-
tion. For example, the following Get unique command is to retrieve a Loan Bal-
ance segment of a loan with the loan contract number 277988 and loan balance
date of July 22, 1996.