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Oracle Instance Recovery Tutorial
Module 4 - Physical and Logical Corruption
>> Dave: What about corruption caused by physical damage?
>> John: Corruption caused by physical damage, that's out of the DBA's and Oracle's control.
That physical damage, we can guarantee zero loss of data provided the database is properly
configured in terms of archivelog mode backup, Data Guard even, but the recovery from physical
damage is not going to be automatic. So we guarantee it, but it isn't automatic.
[pause]
>> Dave: Guaranteed as long as we've done proper administration with backups?
>> John: And if we haven't, you fire your DBA. That's usually the management's immediate
reaction to an Oracle database losing data.
[pause]
>> Dave: Very good. One more question. What about logical corruption or bad block formats?
>> John: Logical corruption again is out of Oracle's control. But from release 11g we
can in fact repair logical corruption automatically but only if you are in the Data Guard's environment
with active Data Guard configured. That's really a bit out of scope for the database.
It's damaged beyond the database's control but we can in fact repair that automatically
through the active Data Guard mechanism. If a logically corrupted block is detected in
the primary database, it will be restored and recovered using a block from the standby
database and the other way around as well.