VSAM with non-RLS access does not ensure read integrity across splits for non-RLS access to a data set with cross-region share options 2, 3, and 4. If read integrity is required, the application must ensure it. When KSDS CI and CA splits move records from one CI to another CI, there is no way the writer can invalidate the data and index buffers for the reader. This can result in the reader not seeing some records that were moved.

VSAM RLS can ensure read integrity across splits. It uses the cross-invalidate function of the CF to invalidate copies of data and index CI in buffer pools other than the writer's buffer pool. This ensures that all RLS readers, DFSMStvs, CICS, and non-CICS outside DFSMStvs, are able to see any records moved by a concurrent CI or CA split. On each GET request, VSAM RLS tests validity of the buffers and when invalid, the buffers are refreshed from the CF or DASD.