ORA-01012
not logged on
Cause
A host language program issued an Oracle call other than OLON or OLOGON, without being logged on to the Oracle. This occurred when a user process attempted to access the database after the instance it was connected to terminated, forcing the process to disconnect.
Action
Log on to Oracle by calling OLON or OLOGON before issuing any Oracle calls. When the instance has restarted, retry the action.