Oracle7: OSOPER and OSDBA on a sequent

Does anyone know how to use OSOPER or OSDBA? My site is running Oracle7 (don't know the exact version number -- 7.0.15 something) on Sequent machines running DYNIX/ptx, and I can't figure out how to get OSOPER or OSDBA to work. According to the Sequent-specific documentation set, all I need to do is create a UNIX group called "ora_<sid>_<role>" and put users into the group; then they will be able to connect to the database with the given SID and will have the appropriate privilege level. According to the Oracle7 Admin guide, it *sounds* as though these connections are made via "connect internal" -- that is, when a user tries to "connect internal", oracle will try first to enable OSDBA, then (if that fails) try to enable OSOPER, based on the user's group id. But when I try to connect internal to the "devl" database and am in the "ora_devl_osoper" or "ora_devl_osdba" group, it fails.

So -- anyone know how to use these roles? Thanks for any help.