This section describes how you can use BRBACKUP to back up large Oracle databases to tape. BRBACKUP calls cpio or dd to copy individual database files from disk to tape. As a result, throughput is largely determined by cpio or dd.
Note the following restrictions for backup with BRBACKUP:
? As the database server is working with high load during the backup, we recommend you to reduce other activities on the computer to the absolute minimum during the backup. Virtually all of the computer's resources ought to be available for the backup.
This clearly limits the high availability required of the SAP System. However, there is no simple solution to this conflict.
? Be aware of the features of hardware compression if you decide to use this.
? No cpio continuation mechanism is supported during parallel backups. For more information, see cpio Continuation Tape. This means that you must always completely save individual files to one volume. Always perform tape swapping with BRBACKUP. Therefore, the size of a file to be saved must not exceed the tape capacity. If you work with tape units with hardware compression, the size of the compressed file must not exceed the tape capacity. Make sure that the tape capacity is not set too high, in order to avoid reaching the physical end of the tape.
? Since individual files can only be written in their entirety to a volume, there is a certain amount of wastage when distributing the files to the available tapes. That is, the tape capacity cannot be fully used. When distributing the files, BRBACKUP makes sure that the tape capacity is never exceeded. The size of the tape header files – that is, label, init<DBSID>.ora file, and init<DBSID>.sap file – and the log files at the end of the tape (central, detailed, and summary log) are not taken into account.
BRBACKUP offers the following functions for optimal backup of large databases:
? BRBACKUP can back up in parallel to multiple mounted tape units (up to 255).
? In a parallel backup, BRBACKUP also supports automatic tape changers. Therefore, a completely automatic backup is also possible with tape swapping for one or more tape units during a backup.
? All files to be saved are distributed to the tape volumes inserted in the tape units. BRBACKUP has different optimization targets. For more information, see Optimization of File Distribution.