Friday, May 22, 2009

Logical vs Physical Standby database

Logical vs Physical Standby database:
The primary functional difference between logical and physical standby database setups is that:

Physical standby database: This is always an exact structural duplicate of the master database.
Logical standby database: Permits you to add additional objects (tables, indexes, etc) to the database.
Logical standby database: Logical standby is based on newer technologies (logical standby is new in Oracle 9.2) and tends to be generally regarded as more tempramental than physical standby.

Physical standby database: This is physically identical to the primary database on a block-for-block basis. It's maintained in managed recovery mode to remain current and can be set to read only. Archive logs are copied and applied.
Logical standby database: This is logically identical to the primary database. It is updated using SQL statements.

Physical Standby database: Achieved by copying the archivle log files.
Logical Standby database: Makes the dml statements using archivelogs generated and applies to the secondary database.

Physical Standby database: Archived redo logs and FTP'ed directly to the standby database which is always running in "recover" mode. Upon arrival, the archived redo logs are applied directly to the standby database.
Logical standby database: This uses LogMiner techniques to transform the archived redo logs into native DML statements (insert, update, delete). This DML is transported and applied to the standby database.
Logical standby database: This can have additional materialized views and indexes added for faster performance.

Learn more how to create physical or logical standby databases for your enterprise.

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