Can CA Datacom databases be allocated as SMS Extended Format datasets?
As noted in the z/OS 2.2 version of the IBM DFSMS Using Data Sets manual (DGT3D410), Extended-Format Sequential Data Sets cannot be accessed using EXCP. CA Datacom uses EXCP processing for all database data and index areas (as well as the CXX, LXX and FXX), so these files cannot be defined as Extended-Format.
The reason for this exclusion is that extended format changes the internal structure of the data records, and the actual records will not match the DCB characteristics of the dataset. Also the internal structure of the blocks is changed slightly, so an EXCP-based program would not be able to read the dataset correctly.