Wednesday, February 10, 2010

RMAN Active Duplicate Advantages


We are planning to start upgrading some of our enterprise Oracle databases from 10g to 11g and I am evaluating the new features of Oracle 11g that our organization can be benefited from. A 11g new feature that has caught my attention is the 'ACTIVE Database Duplicate' option in Oracle RMAN. This feature allows a database to be duplicated directly from its live source database instead of using its backup.

Instant Database Clones possible (On Demand Cloning)

If one requires a database clone, all one has to do is to run the active database duplicate command after specifying the source and destination databases. I call this Cloning onDemand ! This helps organizations create test database environments in a rapid and simpler fashion.

EMC TimeFinder BCV sync/split is not necessary

Consider an organization relying on BCV sync/split technology to perform database clones. In this case one must take the help of a system administrator to perform the BCV sync/split operation. A database is put in hotbackup mode and the BCV split process is performed. Once the operation is completed, the database is taken out of backup mode. This is all additional work and the Active Database Duplication eliminates all these steps as it performs a direct copy.

Staging ASM Diskgroup is not required

Consider the case when ASM (Automatic Storage Management) is used as the underlying disk management technology for an Oracle database. An ASM-2-ASM database clone always requires a consistent BCV sync/split operation and this during process the ASM disk headers are copied to the destination host. This requires staging (intermediate) ASM Diskgroups on the destination host with the same name as that of the source database's ASM diskgroups. After the consistent BCV sync/split is completed, data is again copied from the staging ASM diskgroups to the clone database's diskgroups(DEV/TEST diskgroup names). Active Database Duplication eliminates the need for staging ASM diskgroups, thus saving a lot of diskspace (equal to the total size of the database being cloned)

No additional space required

In the traditional backup-based database duplication, one has to make the backups accessible to the destination host before the duplication is started. For tape backups, this equates to moving the tape to a drive attached to the destination host or using a network-accessible tape server. For disk backups, this equates to copying the backup to the destination host (additional space). Active Database Duplication does not require backups and hence the additional disk space requirement is no longer needed on the destination host.


Incomplete recovery NOT possible (no SET UNTIL)

Active Database Duplication cannot be used to duplicate a database until a point in time. One has to rely on the backup-based database duplication method if one wants to create a duplicate database until a specific point in time ( a specific time, log sequence or SCN). Furthermore, active duplicate copies data only until the last archived log file in the source database. The contents of the online redologs will not be copied to the duplicate database.

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