VSAM alternate index the Real Advantages

The alternate index is used to access records other than base key. The dataset over which alternate index defined is called base cluster.


  • Can be defined for both KSDS and ESDS
  • reduce data redundancy
  • Can have duplicates
  • Easy to define using IDCAMS
  • allow datasets to be accessed by both sequentially and randomly
VSAM alternate index merits
Image courtesy|Gettyimages.in


  • Performance degradation
  • Complex update logic

Also Read:

Author: Srini

Experienced software developer. Skills in Development, Coding, Testing and Debugging. Good Data analytic skills (Data Warehousing and BI). Also skills in Mainframe.