Backup Device Management 
Backup Device Management
An essential part of a backup strategy is the management of storage devices. You need to decide:
Type of Backup Media
You can choose to backup either to tape or to disk. Usually tapes are used because they are less expensive and easier to handle.
If you decide to back up to tape, the tape device must be connected directly to the computer on which the SQL Server is running. DLT tapes are preferable to DAT tapes as they offer more security and have a greater capacity.
The term tape backup device refers to a tape device. When the R/3 System is installed, three tape backup devices are automatically created; R3DUMP0, R3DUMP1, R3DUMP2.
If you decide to backup to disk, SQL Server supports both local and network backup devices. A local device is a file on a local computer. A network backup device is a file on a shared network directory.
For instructions on how to backup to disk, refer to the SQL Server Books Online.
Expiration Period
Set the expiration period to 28 days. This means the backup cannot be overwritten for 28 days. Both the SQL Server Enterprise Manager and the R/3 Planning Calendar provide options to protect tapes or disk backup devices from being overwritten during the backup cycle.
Keep the last database backup of each month for a year and the last database backup in the financial year permanently.
Use at least two tape sets in rotation so that the last two backups are always available.
Number of Tapes Required
The number of tapes you need depends on:
Work out the necessary capacity on the basis of the transaction log volume, the data volume and add approximately 30% to allow for database growth.
You are strongly advised to use 2 tapes per day; one for the database backup and one for the transaction log backup.
Tape Names
If you use the tape naming conventions that SAP recommends, you can identify the contents of a tape simply by looking at the label. Always make sure that the correct name sticker has been placed on the tape cartridge before you insert it into the tape device.
Tape labels used by SQL Servers have up to 128 characters. SAP recommends a naming convention with 5 or 6 characters. The characters have the following meaning:
R R/3 database
M msdb database
S master database
C combination of databases
Other databases in the SAP environment may be indicated with other characters.
D full database backup
DD differential database backup
L transaction log backup
Do not mix transaction log backups and database backups on one tape.
A device no. 1
B device no. 2
C device no. 3 and so on
When only using one device (no parallel backup), the last character is always set to A, even if the backup extends across more than one tape.
RD15A denotes the first tape (A) of an R/3 (R) database backup (D) on day 15 of the month.
The label RL05B shows that the tape contains an R/3 transaction log backup. The backup was performed on day 05 of the month. The B denotes that it is the second tape of a parallel backup.
Storing a Backup on Multiple Tapes
If the database backup no longer fits on one tape, there are two ways of distributing the backup data to several tapes:
Using this procedure, a database backup is written to two or more tapes sequentially using a single tape device.
SAP does not recommend this method. It is better to use tapes with a larger capacity so that a database backup fits on a single tape. This makes it easier to administer tapes in a backup cycle and simplifies the restore procedure.
Keep in mind that if large quantities of data are involved, backing up sequentially takes a very long time. If one tape is insufficient for the backup, rather schedule a parallel backup in the R/3 Planning Calendar.
Several tape devices are required for a parallel backup. The data that is dumped is divided evenly among the tapes. Parallel backups require less time than sequential ones, but may create a greater system load. Note that a parallel backup can only be executed if you have an additional backup device.
See also:
Backing Up with R/3