This section discusses how you can speed up a backup of your Oracle database. Backups can often take a long time. For example, if you use digital audio tape (DAT) devices as a backup medium, you can back up 8 to 12 GB per hour, using hardware compression. This means that backing up a 50 GB database on one tape device of this type takes approximately five hours.
You can improve throughput by performing data backups in parallel. If you have several backup devices, you can make a parallel backup with BRBACKUP by assigning several tape devices to the init<DBSID>.sapparameters tape_address and tape_address_rewind or several disks to parameter backup_root_dir. You can then make a backup of, for example, a 100 GB database in parallel on five tape devices in three hours.
If you are using the logical volume manager (LVM), a logical volume is considered to be one disk. Therefore, you should not distribute a logical volume to be used for backup over several physical disks when this is not absolutely essential.
By keeping the logical volume on one physical disk, you minimize read/write head movement on the disk, so speeding up the backup.
A good way to reduce backup time is to perform a two-phase backup:
1. You back up to disk, using the backup_dev_type parameter.
2. You copy the disk backup to a tape volume, using the tape_copy_cmd. You can assign the copy operation a lower priority.