Information Systems

VSAM is a high-performance access method used in OS/VS & ZOS operating systems. VSAM software resides in virtual storage along with the program that needs its services for the manipulation of data on a direct access storage device (DASD).
VSAM acts an interface between Operating system and application program
The access method is used to organize data and maintain information about the data in a catalog
Catalog management: The catalog contains information about data sets
Record management: VSAM data sets can be defined and catalogs can be established using a multifunction services program called AMS (Access Method Services)
• VSAM is Virtual Storage Access Method
• VSAM is a high-performance access method used in OS/VS and ZOS operating systems
• It is a method used to move data between disk and main storage
• VSAM operates in virtual environment
• VSAM acts as interface between operating system and application program
• All VSAM data sets reside on DASD devices
• All data sets must be defined in a catalog
VSAM does more than just replace non-VSAM access methods with VSAM access methods
• It also provides efficiency improvements and a comprehensive catalog facility that centralizes information about all VSAM data sets
• In addition, the multi-functional utility program – AMS – has a variety of file related functions for VSAM as well as non-VSAM files