Split Mirror Backup 
This section describes how you can use split mirror disk backup with BRBACKUP to perform an online or offline backup of your Oracle database without downtime. We recommend this especially for online backup of large databases.
Caution
We provide this information on split mirror backup for advice only. Consult your hardware partner for help in setting up split mirror backup.
It is especially important to make sure that the data on the backup database host is consistent when you perform the backup.
Integration
Computing Center Management System (CCMS)
You cannot use CCMS to schedule split mirror disk backups. This is because BRBACKUP runs on the backup database host if scheduled from the DBA Planning Calendar.
However, you can use CCMS to monitor backups on the production system, because BRBACKUP sends status information to the production database, which CCMS can then use.
The BACKINT interface is also supported in the split mirror configuration. This configuration is transparent to BACKINT and there are no extra considerations for BRBACKUP.
A split mirror disk backup only includes database backups with BRBACKUP. Backups of the offline redo log files using BRARCHIVE are not included because they do not place significant load on the production host. In a standard setup, you back up the offline redo log files on the database server to local or remote tape devices, on disk or with BACKINT.
If the backup device is connected to the backup server, you can use the remote device – using backup_dev_type = pipe|pipe_auto|pipe_box – or the BACKINT interface.
To synchronize BRBACKUP sessions with BRARCHIVE sessions, you can start a BRARCHIVE session immediately after the disks are split and not just at the end of the BRBACKUP run. When the disks have been split, Oracle regards the backup as already finished.
You can use RMAN for split-mirror backups, where:
backup_type = online_split|online_mirror|offline_split|offline_mirror
For more information about setting the parameters for RMAN with split-mirror backups, see Profile Parameters and Command Options for init<DBSID>.sap in Split Mirror Backup: Software Configuration.
You can even do level-0 full backups and incremental backups in this way. As a prerequisite you need to make a sure that the sapbackup directory is shared or mounted for the database and the backup server.
CautionTo be able to perform an RMAN backup on the backup server, BRBACKUP sets the database on the backup server to mount state. Therefore, the Oracle server software must be fully installed on the backup server.
End of the caution.You can use split-mirror backups to back up your standby database, but only in offline split mode. You need to first stop the import of offline redo log files. This is the new backup type:
backup_type = offstby_split|offstby_mirror
Similar to the connection definition to the production database in the init<DBSID>.sap parameter primary_db, you also need to define a connection to the standby database as follows:
standby_db = <conn_name>
For more information, see standby_db.
Features
In the split mirror configuration, the disks of the production database host are mirrored, that is, synchronized. BRBACKUP runs on a backup database host, where the backup is performed after the mirror disks have been split and mounted. On the production host, this saves processing power otherwise required for the backup, so that the production SAP System is unaffected by the backup.
BRBACKUP can be used to control the splitting and later synchronization of the disks. If you want to open the database on the backup host and use it as a “reporting server” you can perform the synchronization yourself later.
The actual splitting and later synchronization of disks is executed by a script or program supplied and supported not by SAP, but by the manufacturer of the operating system, disk subsystem, or backup software.
If the split disks do not have to be resynchronized immediately after the backup you can use the backup server along with the mirror disks to operate an independent SAP system on the backup server. For this, you must install the entire Oracle server software on the backup server.
For more information, see the following:
Activities
There are two basic scenarios:
Split Command Scenario
This uses split_cmd and resync_cmd to split and resynchronize the mirror disks. BRBACKUP controls the splitting and later synchronization of the disks.
SPLITINT Scenario
This uses the SPLITINT interface program with split_options and split_resync to split and resynchronize the mirror disks. BRBACKUP calls SPLITINT to actually split and resynchronize the disks. SPLITINT executes the split and resync requests from BRBACKUP using the appropriate disk subsystem calls.
NoteDatabase handling with the SPLITINT scenario is considerably faster than with the split command scenario. This is the recommended approach.
For each scenario, there is an online and an offline variant.
End of the note.
The following graphic shows how split mirror backup works:
Split Mirror Backup
1. |
Tablespaces set to status BACKUP |
Production database shut down |
2. |
Mirror disks (A' and B' in the graphic) split and connected to backup server using: Split command scenario: split_cmd SPLITINT scenario: SPLITINT program |
|
3. |
Tablespaces reset to normal status |
Production database restarted |
4. |
Mirror disks backed up on backup host |
|
5. |
Optional: Primary and mirror disks resynchronized using: Split command scenario: resync_cmd SPLITINT scenario: SPLITINT program |
Recommendation
Consider online split mirror disk backup if high availability is an important consideration for your system.