Typing sqlplus /@db is NOT Single Sign-on but rather logging in to the database(s) as an externally identified user (Oracle identifies the user as being an OS account belonging to the "DBA" group).


For Single Sign-On, you need to install OID (Oracle Internet Directory) which you then can synchronize with the WinDoze Active Directory to support corporate-wide SSO.

Also for the Applications to be able to "use" SSO, they themselves have to have configured (and available) a module/plugin/program that supports SSO.

Good Luck!