Oracle Database 12C Cannot Start After Shutdown

Question

I was able to login to sqlplus with my credentials to do the SHUTDOWN command. It worked and the database shutdown. But now when I try to login again with the same credentials to start the server back up, it says: "ORA-01033: ORACLE initialization or shutdown in progress". How can I log in to sqlplus and use the STARTUP command?

This is on Linux Debian - Oracle 12C.

EDIT: I shutdown the database to import a copy of old oradata contents.

Answer 1

Login with operating system credentials that don't require the database to be open:

C:\>sqlplus / as sysdba

If things are really messed up you might need to connect using the prelim option:

C:\> sqlplus -prelim / as sysdba

If the database is hung and not shutting down properly sometimes you need to do a shutdown abort and then start it back up:

SQL> shutdown abort
ORACLE instance shut down.
SQL> startup

This is also possible with the srvctl command but in my experience it's not as reliable as a SQL*Plus shutdown abort.