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
