VSAM Files in COBOL How to Access them

Here are ideas on how to access VSAM files in COBOL.

VSAM File Features

1. Entries in Master or User catalog is possible for VSAM datasets.
2. In general, the Master catalog and User-catalog both can have entries of VSAM and non-VSAM datasets.
3. Only KSDS datasets have Indexed. ESDS and RRDS do have only the data components. That means they do not have an index.
   1. |Data component|Index component|
4. While working with ESDS and RRDS you no need to use index.
5. KSDS has an index is a combination of Key and Value. KSDS also supports an alternate index.
   1. Index key|Sequence value
6. In KSDS first, it locates the index, then finds corresponding sequence value later it get data from control interval and area.
7. The catalog that stores both VSAM and non-VSAM datasets information is called the ICF integrated catalog facility.

How to access VSAM files in COBOL

SELECT TEST1 ASSIGN TO TEST1
               ORGANIZATION IS INDEXED
               ACCESS IS RANDOM
               RECORD-KEY IS TS-EMPLOYEE-NUMBER
               ALTERNATE RECORD KEY IS TS-SOCIAL-SECURITY-NO
               ALTERNATE RECORD KEY IS TS-DEPT-NO
                         WITH DUPLICATES.

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