Components

Components (for Beginners)

Summary

For basic information, go through the Components (for Experienced)

A component is an individual part of a VSAM dataset. Each component has an entry, a name in the catalog, and an entry in the VTOC.

VSAM dataset has three components, and those are -

  • Cluster
  • Data component
  • Index component

For example - Assume MATEGJ.TEST.VSAM is the VSAM KSDS file created.

MATEGJ.TEST.VSAM			-	Cluster Component       
MATEGJ.TEST.VSAM.DATA		-	Data Component
MATEGJ.TEST.VSAM.INDEX		-	Index Component
Note! VSAM does not allow JCL concatenation between two VSAM components.

Cluster -

A VSAM cluster is a logical definition for a VSAM dataset and has the below one or two components -

  • The data component contains the data records.
  • The index component of the key-sequenced cluster consists of the index records.

IDCAMS DEFINE CLUSTER access-method services used to define VSAM datasets (clusters) with data and index components.

For example - Assume MATEGJ.TEST.VSAM is the VSAM file created.

MATEGJ.TEST.VSAM			-	Cluster Component

Data Component -

  • VSAM Data Component contains data records. These data records can be small or large that might spread across CIs and CA.
  • Every VSAM file type (ESDS, KSDS, RRDS, VRRDS, LDS) has a data component.
  • The data component is part of the VSAM dataset, alternate index, or catalog.

For example - Assume MATEGJ.TEST.VSAM is the VSAM file created.

MATEGJ.TEST.VSAM 
MATEGJ.TEST.VSAM.DATA		-	Data Component

Index Component -

  • The index component contains index records with the key fields/RBA of data records.
  • VSAM can randomly retrieve the record from the data component using the index.
  • KSDS and vRRDS only have the index component.

For example - Assume MATEGJ.TEST.VSAM is the VSAM KSDS file created.

MATEGJ.TEST.VSAM
MATEGJ.TEST.VSAM.DATA
MATEGJ.TEST.VSAM.INDEX		-	Index Component

Component Example