You synchronize a
logical standby database with the primary by transforming the redo data into SQL statements that
are executed against the standby database.
Physical and logical standby databases serve different purposes. A physical standby database
is a block-for-block copy of the primary database, so it can be used for database backups in place
of the primary database. During disaster recovery, the physical standby looks exactly like the
primary database it replaces.
A logical standby database, because it supports additional database structures, can more
easily be used to support specific reporting requirements that would otherwise burden the primary
database. Additionally, rolling upgrades of primary and standby databases can be performed with
minimal downtime when logical standby databases are used. The type of standby to use depends
on your needs; many environments start out using physical standby databases for disaster recovery
and then add in additional logical standby databases to support specific reporting and business
requirements.
NOTE
The operating system and platform architecture on the primary and
standby locations do not need to be identical as of Oracle Database
11g. The directory structures for the primary and standby databases may
differ, but you should minimize the differences to simplify administration
and failover processes. If the standby is located on the same server as
the primary, you must use a different directory structure for the two
databases, and they cannot share an archive log directory.
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