Oracle Database Error | ORA-12528

Question

When I try to connect to my Oracle database, I get Listener refused the connection with the following error: ORA-12528, TNS:listener: all appropriate instances are blocking new connections. Also, I'm not sure if this means anything but I checked and my database is not mounted.

Answer 1

If the "unregister" did not complete properly, then when you go to "startup" the next time, since the LISTENER did not unregister the instance, you receive the error, "ORA-12528: TNS:listener: all appropriate instances are blocking new connections" since an "appropriate" instance is already running.

Check the status of the listener by

LSNRCTL> status

One method that should resolve this problem is to restart (bounce) the LISTENER:

LSNRCTL> stop LSNRCTL> start

Then restart your instance: sqlplus with sysdba privileges

SQL> startup

Make sure all parameters are set.