VSAM Essentials Workshop

This hands-on course describes and explains the access method concepts in MVS and the structure and design of VSAM files. It teaches how to create VSAM files using the utility Access Method Services (AMS), both from a functional as well as a performance point of view.
Additionally, it provides the Systems Programmer and Operational Analyst with information on the structure of ICF catalogs and the related VTOC and Index VTOC.
Online exercises provide experience in creating, accessing and managing VSAM files. Attendees will create and use clusters, alternate indexes and paths.

This course is also available for exclusive, one-company presentations and for live presentation over the Internet, via the Virtual Classroom Environment service.

Virtual Classroom Environment dates - click to book!

UK Start Times

10 July 2024 30 September 2024

What is a 'Virtual Classroom Environment'?


What do I need?

  • webcam
  • headphones with microphone
  • sufficient bandwidth, at least 1.5 Mb/s in each direction.

What you will learn

On successful completion of this course you will be able to:

  • describe and explain the concepts of the z/OS access methods
  • analyse the structure of the RRDS, ESDS, KSDS and LDS data sets
  • use the Access Method Services utility program IDCAMS to define, load, backup, monitor and manipulate VSAM data sets with particular emphasis on the KSDS file type
  • develop guidelines for optimised allocation of VSAM files for use at their installation
  • identify performance related issues in the batch and online environments that can be found when using the KSDS file type.

Who Should Attend

All programmers, systems programmers, operators and operations analysts.


Familiarity with basic z/OS principles and a working knowledge of TSO/ISPF and JCL.


3 days

Fee (per attendee)

£1750 (ex VAT)


This includes free online 24/7 access to course notes.


Hard copy course notes are available on request from rsmshop@rsm.co.uk

at £50.00 plus carriage per set.

Course Code



VSAM Overview

MVS and I/O processing; The access methods; The IOS Drivers; The I/O Supervisor (IOS); The Back-End process; MVS access methods; Queued Sequential Access Method; Basic Direct Access Method; Basic Partitioned Access Method; PDSE processing; And now to VSAM; VSAM features; Entry Sequenced Data Set (ESDS); Key Sequenced Data Set (KSDS); Relative Record Data Set (RRDS); Catalog concepts; ICF catalogs and VTOCS; ICF catalogs (BCS); VSAM Volume Data Set (VVDS); Cluster Catalog (BCS) entries; Alternate indexes and paths; VSAM overview - exercises.

VSAM Dataset Structure

Control Areas; Control Intervals; Control Interval structure; CI structure of fixed length records; CI structure of variable length records; Control Area structure ; elative Byte Address; Spanned records; Storage of data on DASD volumes; Entry Sequenced; Key Sequenced; Index component; Free space; RRDS characteristics; KSDS processing example; The Control Interval is rewritten; Deleting a record; Record insertion; CI split; CA split; VSAM dataset structure - exercises.

Using Access Method Services

Access Method Services (AMS); AMS command format; Example - define an ESDS; Modal commands; Cancelling IDCAMS steps; Using the ELSE and SET commands; Comments; Error messages; Dataset already exists.

Defining VSAM Datasets

IDCAMS commands; DEFINE command - main parameters; Defining a cluster; Cluster sub-parameters; IDCAMS required parameters; Space allocation and reuse; SHAREOPTIONs (x region, y system); Control Interval Size; More IDCAMS parameters; DATA and INDEX sub-parameters; Defining an ESDS; Defining an RRDS; Defining a KSDS; FREESPACE; DELETE MASK | NOMASK.

Listing Catalog Information

Listing catalog information - LISTCAT; Catalog information; LISTCAT; LISTCAT parameters; LISTCAT examples; LISTCAT output.

VSAM Dataset Management

VSAM data management commands; Loading datasets; REPRO; REPRO parameters; Copy ESDS to KSDS; Copy partial RRDS to RRDS; Copy keyrange from KSDS to KSDS; Merge two KSDSs; Copy KSDS to tape; Printing datasets; PRINT parameters; PRINT examples; PRINT output example - CHARACTER; Altering catalog entries; Deleting catalog entries; DELETE parameters; DELETE examples.

Alternate Indexes

Why use alternate indexes?; Alternate index design; Alternate index record; Defining a route to the base cluster; Update of an alternate index; Defining an alternate index; Alternate index sub-parameters; Alternate index (SMS); AIX record size calculation; Building an alternate index; Defining a Path; Printing a base KSDS; Printing via an alternate indexes using PATH.

VSAM Data Integrity

Data integrity; Disposition processing; VSAM SHAREOPTIONS; Cross system sharing; VSAM back-up options; The EXPORT command; VSAM recovery options; The IMPORT command.

VSAM Performance Considerations

What to tune; Record design considerations; Data CISZ and performance; CI% freespace; CI FSPC optimisation; Index CISZ considerations; Data CA size considerations; CA% freespace; Component level performance; VSAM buffers; Index component buffers; Optimum index buffering; Data component buffers; Optimum data component buffering; VSAM buffering techniques; VSAM NSR buffer utilisation; VSAM LSR buffer utilisation; Batch LSR; Is batch LSR the solution?; Batch LSR JCL changes; Additional BLSR SUBSYS parameters; BLSR recommendations; BLSR restrictions; AIX performance considerations.

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