Processing VSAM files
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:
- Protection of data against unauthorized access
- Compatibility across systems
- Independence of devices (no need to be concerned with block size and other control information)
- Simpler JCL (information needed by the system is provided in integrated catalogs)
- Ability to use indexed file organization or relative file organization
The following table shows how VSAM terms differ from COBOL terms and other terms that you might be familiar with.
|Similar non-VSAM term
|Entry-sequenced data set (ESDS)
|QSAM data set
|Key-sequenced data set (KSDS)
|ISAM data set
|Relative-record data set (RRDS)
|BDAM data set
|Control interval size (CISZ)
|Access method control block (ACB)
|Data control block (DCB)
AMP parameter of JCL
DCB parameter of JCL
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, se the VSAM publications for your operating system.
Defining VSAM file organization and records
Coding input and output statements for VSAM files
Handling errors in VSAM files
Protecting VSAM files with a password
Working with VSAM data sets under z/OS and z/OS UNIX
Improving VSAM performance