By using the VSAM JCL parameter RLS, you can specify record-level sharing with VSAM. Specifying RLS is the only way to request the RLS mode when running COBOL programs.
Use RLS=CR when consistent read protocols are required, and RLS=NRI when no read integrity protocols are required. You cannot specify RLS if you allocate your VSAM data set with an environment variable
related tasks
Preventing update problems with VSAM files in RLS mode
Handling errors in VSAM files in RLS mode
related references
Restrictions when using RLS