VSAM Record-Level Sharing Considerations

Do not open data sets for record-level sharing (RLS) or DFSMStvs in the user exit. Access method services expects the exit to use only non-RLS access. Set the high-order bit of byte X'19' in the ACB to prevent a potential JCL DD override that specifies RLS processing. For example:

  OI    ACB1+X'19',X'80'              SET ACBNOJCL FLAG

If the data set that is being opened is currently open for RLS or DFSMStvs access, the non-RLS open fails. If the data set has previously been opened for RLS or DFSMStvs access, but requires recovery, a non-RLS open for input is allowed. However, open for output fails.