Objectives

This 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.

Students learn to:

• Analyse the structure and uses for RRDS, ESDS, KSDS, and LDS VSAM data sets.
• Use IDCAMS commands to create, monitor, and manipulate VSAM data sets.
• Develop guidelines to allocate VSAM files to minimise disk usage and optimise CPU utilisation.
• Diagnose problems in VSAM data sets using knowledge of the internal structure of VSAM data sets, components, and control fields.

Main topics

• VSAM overview

MVS and I/O processing; MVS access methods; VSAM terminology; VSAM dataset structures: ESDS, RRDS, KSDS, linear datasets; ICF catalogs and VTOCs.

• VSAM data set structure

Control Areas; Control Intervals; CI structure ppanned records; CI splits; CA splits.

• Using Access Method Services

Modal commands; creating VSAM clusters; Modal command examples; error messages.

• Defining VSAM data sets

Define command; define cluster parameters; space allocations; defining ESDS, KSDS & RRDS.

• Listing catalog information

Listcat command; listcat options.

• VSAM data set management

Management commands; REPRO; REPRO options; copying & merging.

• Alternate indexes

Defining an AIX; BLDINDEX; UPGRADE vs UPDATE; using AIX.

• VSAM data integrity
• VSAM performance considerations

IMBED; bufferspace; KSDS space requirements; NSR; LSR.

• Problems, diagnostic tools and repair tips

Problems; VSAM JCL; file I/O problems; diagnostic tools; damaged data.