ORA-01012: not logged on

Symptom

> sqlplus "/ as sysdba"
SQL*Plus: Release x.xx.xx - Production on
Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.
Connected.
SQL> select instance_name from v$instance;
select instance_name from v$instance
*
ERROR at line 1:
ORA-01012: not logged on

Solution

1. This is just workaround since no errors are detected from the alert log. Login to the database as sysdba and perform shutdown abort

SQL> shutdown abort

Alternatively, you can kill the Oracle instance processes.

pkill –u USERNAME
ps –ef | grep ORASID
kill -9 PIDS

2. Stop the Oracle listener.

3. Start the listener and your database again.

SQL> startup