Course Abstract,

Audience, and



DASD File Design and Tuning using VSAM

Updated 15 November 2003
The Virtual Storage Access Method is a collection of interfaces, commands, and structures along with the programming subsystems that implement them, for storing and retrieving data on disk (sometimes referred to as DASD, for Direct Access Storage Devices) in IBM e-server mainframe systems, such as VSE, zVM and zOS.

This class focuses on the VSE/VSAM implementation, used by many thousands of mainframe server systems and indirectly by millions of users of these systems. IBM reports that over 80 percent of the data storage in VSE operating system environments is managed by VSE/VSAM.

20 to 40 percent reduction in CPU time and in I/O activity for critical jobsteps and on-line transactions is typically experienced when the principles taught in this class are implemented. This reduction in CPU time and in I/O activity is directly translated into additional system capacity for other work. Although individual results will vary, the reductions in system resource load make more capacity available for other system needs immediately. Reducing the load from higher priority jobs will add to the resources available to do other work. Lower priority jobs within the system will experience the largest improvements in their run times as more resources become available for them.

Experience has shown that over 80% of the potential performance improvement for any given workload is achieved through application of the principles taught in this class and shown in its laboratory exercises without any change to application programs. Thus, this class is applicable even for "package solutions" from outside vendors.

This class has been designed to meet the needs of Systems Professionals, including:
  • System Programmers
  • System Architects
  • Application Designers
  • Application Programmers
  • Data Base Administrators
  • and others,
who design, implement, or tune systems and applications which use the Virtual Storage Access Method to store and retrieve their data.
Course Objectives
Upon completion of this course, the student should be able to:
  • Identify characteristics of various hardware implementations of direct access storage subsystems.
  • Identify performance impact expected from different caching and buffering strategies.
  • Identify file structures suitable for a given application need.
  • Choose optimum file organizations and other characteristics based on application specifications.
  • Calculate DASD space requirements for files.
  • Specify file placement for optimum performance.
  • Create VSAM definition, initial load, backup and restore, and diagnostic jobs.
  • Evaluate performance requirements for a VSAM file and job.
  • Define required data integrity, backup and recovery features for catalogs, files and jobs.
  • Measure system resource consumption and make tuning recommendations based on those measurements.
  • Evaluate applicablilty of VSE/VSAM (or other vendor implementations of) Space Compression for specific files.
  • Identify and evaluate vendor utilities for the VSE/VSAM environment.
Course Methodologies and Materials
The course will be taught using a combination of classroom lectures and practical laboratory work. Live, current level VSE/ESA systems provide an environment for numerous hands-on machine exercises where students can evaluate the results of what they have learned. A student notebook will be provided.
This course has been developed by and will be taught by Dan Janda (The Swami of VSAM), who has been working with VSAM in IBM laboratories and the real world for over 30 years. Dan has been a frequent speaker on VSAM, VSE, CICS, and performance topics at WAVV, GUIDE, CMG and other user group meetings and IBM technical conferences around the world. You can visit his web site at
Schedule and Location
It is our intention to keep course expenses (travel, hotel, etc.) reasonable. This course is offered in conjunction with CPR Systems. You can visit CPR's web site at to identify offering times and locations, as well as registration and fee information.

Customized and on-site offerings are available. Contact The Swami for more information.

The Swami
The Swami


CPR Systems
CPR Systems

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