I have the following problem.
I just install new Oracle 8.1.7 database server and
I am getting "ORA-01031: insufficient privileges " when I am using the following command:
SQL*Plus: Release 18.104.22.168.0 - Production on Wed Apr 24 16:07:49 2002
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ORA-01031: insufficient privileges
However "sqlplus internal" works fine.
I can tnsping prod.
You must have SYSDBA privilege in order to 'connect internal'. The ORA-01031 error is telling you that you do not have this privilege context, so it will not permit the connection.
The difference between the two connections you describe is that one is specifying a database that must be listed in your naming service (local naming or Oracle Names), and that database can reside on another machine. The other tells SQL*Plus to obtain information about the database--especially the database SID--from the O/S environment.
You did not mention whether 'prod' was on the same or another server. If it is on another server (from where you are running SQL*Plus), then SYSDBA privileges are not automatically available remotely in this way. They have to be setup. If it is on the same server, then you obtain SYSDBA privilege by using an O/S user account that is a member of the DBA or ORADBA group. (Group name is O/S dependent.)