Oracle A423961 - Manual (Page 95)

4 – 11 Getting the Most out of Integration with Windows NT
username being NTUSER2), then the following takes place when the
user issues the command
SVRMGR> connect / as sysdba
Oracle will search for the username NTUSER2 in group
ORA_ORCL_DBA. If found, the user will be given DBA privileges. If
not found Oracle will check the global group ORA_DBA.