Consistent Processing Options

To be compatible, both the new ACB and the existing control block structure must be consistent in their specification of the following processing options.

The data set specification must be consistent in both the ACB and the existing control block structure. This means that an index of a key-sequenced data set that is opened as an entry-sequenced data set, does not share the same control block structure as the key-sequenced data set opened as a key-sequenced data set.
The MACRF options DFR, UBF, ICI, CBIC, LSR, and GSR must be consistent. For example, if the new ACB and the existing structure both specify MACRF=DFR, the connection is made. If the new ACB specifies MACRF=DFR and the existing structure specifies MACRF=DFR,UBF, no connection is made.

If compatibility cannot be established, OPEN tries (within the limitations of the share options specified when the data set was defined) to build a new control block structure. If it cannot, OPEN fails.