Rational Developer for System z
Enterprise COBOL for z/OS, Version 4.1, Programming Guide


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:

The table below shows how VSAM terms differ from COBOL terms and other terms that you might be familiar with.

Table 1. Comparison of VSAM, COBOL, and non-VSAM terminology
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


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