The system carries out a backup action at regular intervals for the most important database information. This backup action is known as a savepoint.
It writes all changed pages held in the data cache to the data area.
· The data cache contains, among other things, the undo log files. As these are also permanently backed up to the data area by a savepoint, the database instance can be restored to a transaction-consistent state in a restart.
· At the time of a savepoint, the data of all open transactions is written to the transaction file.
See also log concept in Background Knowledge: SAP DB.