VSAM Tutorial



  1. Concept
  2. Cluster Type
  3. Control Interval
  4. VSAM Catalogs
  5. VSAM Data Space
  6. Non VSAM Data Space


  1. Access Method Services.
  2. Programing Syntax (VSAM).
  3. VSAM Modal Comands.
  4. VSAM Examples.
  5. Interview Questions.



Virtual Storage Access Method - VSAM - is a data management system introduced by IBM in the 1970s as part of the OS/VS1 and OS/VS2 operating systems.  Although there are still datasets that are best managed with the several other (non-VSAM) data management methods, VSAM is a major component of modern IBM operating systems.  Since MVS 3.8 is one of those operating systems, I thought it might be useful to other Hercules' users to set down some basic information about VSAM.

I have divided the material presented here into two main segments -

  • Concepts and Facilities
  • Access Method Services

In the first segment, I will try to provide a simple description of the components of VSAM, with the goal of introducing VSAM to those who have not had practical experience with it.  I don't want to write a textbook, as I have several of those in my own library and they can be quite dry and boring.  But, it is my perception that quite a few people are coming into the Hercules (and MVS) community who have not had any formal exposure to this type of material and I think there may be some positive benefit to my efforts.

In the second segment, I will try to cover most, if not all, of the functions provided by Access Method Services.  Access Method Services is the single, general-purpose utility that is used to manipulate VSAM components by both Systems and Applications Programmers.  If you are more interested in the "how to" rather than the "why", this second segment is probably where you will want to begin reading.

There is also an index at the left of the page to allow you to quickly locate the section describing a particular AMS function.