When invoked directly as a transaction, DK1TDRVC does not perform any ML commands to set up its library search list (LIB-LIST). Therefore, the site default LIB-LIST is used as the initial library search list.
When invoked by tablesONLINE/CICS, DK1TDRVC picks up the list of concatenated libraries from the current tablesONLINE/CICS list for the user.
In either case, if you wish to work from a library (or VTS subsystem) not on the initial list, your first command should be an ML command to point tableBASE to that library. The current library search list can be checked at any time with the LL command.