The most common causes of Oracle connection errors

1, ERROR:
ORA-12560: TNS: protocol adapter error
 
Listener is not started. start listener: lsnrctl start on the server where the database is located.
 
 
2, ERROR:
ORA-01033: ORACLE initialization or shutdown in progress
 
Oracle is not in the open state and can only be connected with sysdba. This error occurs when a common user connects.
 
 
3, ERROR at line 1:
A ORA-01034: ORACLE not available
 
The database instance was started but not opened. An error occurred while executing the SQL statement after connecting to sysdba.
 
 
4, ERROR:
ORA-03114: not connected to ORACLE
After session connection, the database restarts and you need to reconnect to the database.


Author kkdelta