ORA-01034 ORACLE not available
Cause: Oracle was not started. Possible causes include the following:
The SGA requires more space than was allocated for it.
The operating-system variable pointing to the instance is improperly defined.
Action: Refer to accompanying messages for possible causes and correct the problem mentioned in the other messages. If Oracle has been initialized, then on some operating systems, verify that Oracle was linked correctly. See the
platform-specific Oracle documentation.
On the practical side, when your server restarts, the database may not have started completely. Do the following
SQL>connect / as sysdba
If database is already started, shut it down and start it again.
SQL>shutdown immediate or SQL>shutdown abort
You can also use the following methods to connect
SQL>connect as sysdba
Provide internal as username.
Make sure listener and database services are running in services. If not start them. If some error, remove configurations in Net8 and try again and you will be successful. This should be done at the top actually. I sincerely hope this solves your problem.