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
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