Backup Device Management

An essential part of a backup strategy is the management of storage devices. You need to decide:

What type of backup media is to be used, for example, disks or tapes
How long tapes should be saved before they are overwritten
How many tapes are needed and their capacity
How tapes should be labeled
How backups that need more than one tape should be organized

Type of Backup Media

You can choose to back up 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 are more reliable and offer a greater capacity.

Note

The term tape backup device refers to a tape device. When the SAP system is installed, three tape backup devices are automatically created, R3DUMP0, R3DUMP1, R3DUMP2.

If you decide to back up 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 back up to disk, refer to the SQL Server Books Online.

Expiration Period

Transaction log, full database backups and differential database backups
Set the expiration period to 27 days. This means the backup cannot be overwritten for 27 days. Both the SQL Server Management Studio and the DBA 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.
Complete Windows system backup
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:

The number of days in the backup cycle
The number of tapes required for the various database and transaction log backups of the day.
Note
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:

Character 1 identifies the database on the tape	Single Database: S: Master database backup M: msdb database backup R: SAP database backup U: User databases backup
Character 1 identifies the database on the tape	Multiple Database: C: Combination (SAP database not included) I: Combination (SAP database included)
Character 2 identifies the type of backup	L: Transaction log backup D: Database backup +: Differential database backup Note Do not mix transaction log backups and database backups on one tape
Characters 3 and 4 indicate the day of the month	<dd: day of the month>
Character 5 indicates whether it is a parallel or a sequential backup	P: Parallel backup S: Sequential backup

Tip

RD15S denotes a sequential (S) backup of an SAP (R) database backup (D) on day 15 of the month.

The label RL05P shows that the tape contains an SAP (R) transaction log (L) backup. The backup was performed on day 05 of the month. The P denotes that it is a parallel backup.

Storing a Backup on Multiple Tapes

Note

SAP recommends you to test and validate the backup and restore process regularly so that you can restore your database to a correct and consistent state.

If the database backup no longer fits on one tape, there are two ways of distributing the backup data to several tapes:

Sequential backup
Using this procedure, a database backup is written to two or more tapes sequentially using a single tape device.

Caution
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 SAP Planning Calendar.
Parallel backup to several tapes
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.

Caution

SAPrecommends to validate the backup and restore process for both methods.