With a restart, the database system restarts the database, that is, switches it from the ADMIN or ONLINE operational state to the OFFLINE operational state, and then switches it back to the ONLINE operational state.
A restart is necessary, for example, in the following situations:
You have changed a database parameter and the change only takes effect after a restart.
The database was not stopped correctly because the computer was switched off due to a power failure.
For a restart, the database system uses information from the last savepoint (most recent consistent state of the database stored in the volumes), and the log entries still stored in the volumes, in order to bring the database as close as possible to the state it was in when it was switched to the OFFLINE operational state.
For a restart to be successful, the volumes in the database must not be damaged. If a hard disk has been damaged, you must restore the database.
You can also restart the database to a state it was in at a point in time in the past.
Each time the database is started, a copy of the kernel log file is created, and the old kernel log file is overwritten with new information.