VSAM And Non-VSAM DATA Management - IBM Mainframe

There are two rather different data management environments that coexist under MVS—VSAM and non-VSAM. VSAM, which stands for Virtual Storage Access Method, was announced in the early 1970s. It was supposed to eventually replace the older non-VSAM data management functions, which are essentially the same today as they were in the mid-1960s when they were originally developed.

Unfortunately, VSAM was not able to meet all of a typical installation's data management needs. As a result, VSAM and non-VSAM data management facilities coexist on today's MVS systems. Until the release of MVS/ESA, one of the important differences between VSAM and non-VSAM data management was that you could make most of the specifications necessary to create a non-VSAM file using standard JCL facilities.

In contrast, you had to create a VSAM file using a utility program called Access Method Services. The Storage Management Subsystem of MVS/ESA, however, lets you bypass Access Method Services and define VSAM data sets using JCL.


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