DELPHI data is stored both on CASTOR (2 copies) on tape and on EOS. Data access is restricted to members of the Unix group xx. The copy on CASTOR only serves as a backup, and is not meant to be used by users any longer. Tools like fatfind take automatically care of this. delstage are no longer be needed, as no staging of data is required.
The location of the data is controlled by the environment variable DELPHI_DATA_ROOT. If you have a local copy of the data (eg at a participating external site), just point it to the top directory of where it is located locally, and things should work.