All modifications to the database contents are logged in the
devspace of a database instance to ensure that the database can be restored if a media device fails.The whole
log area may comprise several log devspaces. When installing a new database instance you can configure the number of required log devspaces, and you can add new log devspaces during the running of the database.To ensure that the data on the database is kept safe, you have the option of mirroring the log devspace(s) (set parameter
LOG_MODE to DUAL).During log backups, the content of the log area is copied to a file and the space it originally occupied is released. The backup files are numbered in sequence by the system numbers and are therefore also defined as version files.
The selected size of the archive log devspace should be sufficient for all the changes occurring between two backups to be recorded there.