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There cannot be a more natural plan as keeping an indepen-

dent copy of a critical database at a different location. In 10g

version, a primary database could have maximum 9 standby

database copies at the same time. With 11gR2, it is possible

to feed 32 standby databases simultaneously.

Actually, Active Data Guard technology is based on the data

guard technology, which is being improved since Oracle 8.

Improvement continued with each new version, and it will

most probably continue in future versions.

In our last issue, we briefly mentioned the new features

brought by Oracle 11gR2 version. In this issue, I will try

to provide basic information on Oracle’s disaster recovery

solution, Active Data Guard.

Active Data Guard technology provides automation software

to simultaneously create, monitor and manage standby

databases from a primary database. An Active Data Guard

standby database is an exact copy of the primary database

and is on a “read only” status. Ongoing changes at primary

database are exactly applied to standby databases

without any change. This means that “active

standby database” can be used for works that

bring load to primary database (instant inquiries,

long-running reports, back-up operations, etc.).

This way, primary database can serve all its

capacity to real customers.

Active Data Guard provides an architectural

structure where “standby database” is isolated

from potential errors of the primary database.

Primary database changes are directly sent from

the memory. Therefore, potential I/0 errors at

primary database does not cause errors at standby

databases. Because database software of both

sides are at different locations, they are isolated

from firmware and software corruptions. Oracle

performs corruption controls before applying redo

logs at “standby databases”, and ensures their

physical and logical data consistencies. Hidden

corruptions in connection with potential hardware

errors (memory, cpu, disk, NIC) and data transfer

errors at primary database are detected to prevent

impacts on standby databases.

Active Data Guard

Database Manager