Virtual storage access method (VSAM) is an access method for files on direct-access storage devices. With VSAM you can load files, retrieve records from files, update files, and add, replace, and delete records in files.
VSAM processing has these advantages over QSAM:
The table below shows how VSAM terms differ from COBOL terms and other terms that you might be familiar with.
| VSAM term | COBOL term | Similar non-VSAM term |
|---|---|---|
| Data set | File | Data set |
| Entry-sequenced data set (ESDS) | Sequential file | QSAM data set |
| Key-sequenced data set (KSDS) | Indexed file | ISAM data set |
| Relative-record data set (RRDS) | Relative file | BDAM data set |
| Control interval | Block | |
| Control interval size (CISZ) | Block size | |
| Buffers (BUFNI/BUFND) | BUFNO | |
| Access method control block (ACB) | Data control block (DCB) | |
| Cluster (CL) | Data set | |
| Cluster definition | Data-set allocation | |
| AMP parameter of JCL DD statement | DCB parameter of JCL DD statement | |
| Record size | Record length |
The term file in this VSAM documentation refers to either a COBOL file or a VSAM data set.
If you have complex requirements or frequently use VSAM, review the VSAM publications for your operating system.
related concepts
VSAM files