Specifying access modes for VSAM files

You can access records in VSAM sequential files only sequentially. You can access records in VSAM indexed and relative files in three ways: sequentially, randomly, or dynamically.

For sequential access, code ACCESS IS SEQUENTIAL in the FILE-CONTROL entry. Records in indexed files are then accessed in the order of the key field selected (either primary or alternate). Records in relative files are accessed in the order of the relative record numbers.

For random access, code ACCESS IS RANDOM in the FILE-CONTROL entry. Records in indexed files are then accessed according to the value you place in a key field. Records in relative files are accessed according to the value you place in the relative key.

For dynamic access, code ACCESS IS DYNAMIC in the FILE-CONTROL entry. Dynamic access is a mixed sequential-random access in the same program. Using dynamic access, you can write one program to perform both sequential and random processing, accessing some records in sequential order and others by their keys. Start of changeTo determine if you want to alter the COBOL runtime ACCESS IS DYNAMIC logic path, see VSAM dynamic access optional logic path in the Performance Tuning Guide.End of change