...
1. When you start the database instance in the ONLINE operational state, the result of the check is that the data area and the current log area have different states.
2. When the log entries are imported, the result of the check is that the import sequence is incorrect.
...
1. You must restore the database system by specifying the correct backup version.
2. Import all the necessary log entries in the correct order.
Start the database instance in the ONLINE operating state.
See also:
Database System Concepts, Logging Transactions