When distributing the files to the tapes, BRBACKUP has different optimization targets:

• BRBACKUP attempts to save all files from a hard disk to a volume (tape). As a result, competing hard disk accesses should be avoided, and the number of read/write accesses should be kept to a minimum.

• This mechanism helps to avoid the following problem: When using tape units with hardware compression, the backup time cannot be estimated accurately from the file size or the size of the compressed file. The optimization is carried out therefore from the backup times stored by BRBACKUP.
• The tape capacity in general is not used to its maximum due to temporal optimization (if the optimal backup time is reached for a tape, no further files are saved to this tape, though the tape still has plenty of space left). The total capacity of all available tapes inserted at the same time must therefore significantly exceed the total size of the files to be saved.
• The temporal optimization is cancelled internally if it would cause a tape change (BRBACKUP always attempts to avoid volume changes). In this case, the entire capacity of the tapes is used. As a result, the backup time can vary for individual volumes.

• BRBACKUP always attempts to use all tape units mounted, even if the backup would fit onto a smaller number of tapes. This is done in order to minimize the total backup time.

The one exception is when the number of files to be backed up is less than the number of tape devices.

• BRBACKUP is capable of "learning". The backup times of individual files are stored in the database and used in the next backup for temporal optimization (if this is carried out).

As a result, the changes to backup time are taken into account for individual files. The backup time can change, for example, if the filler level of the individual database files varies and the files should be saved with hardware compression using a tape unit.