A logical standby database takes standard Oracle archived redo logs, transforms the redo records they contain into SQL transactions, and then applies them to an open standby database. Although changes can be applied concurrently with end-user access, the tables being maintained through regenerated SQL transactions allow read-only access to users of the logical standby database. Because the database is open, it is physically different from the primary database. The database tables can have different indexes and physical characteristics from their primary database peers, but must maintain logical consistency from an application access perspective, to fulfill their role as a standby data source.

A physical standby database is physically identical to the primary database. While the primary database is open and active, a physical standby database is either performing recovery (by applying logs), or open for reporting access. A physical standby database can be queried read only when not performing recovery while the production database continues to ship redo data to the physical standby site.

Physical standby on disk database structures must be identical to the primary database on a block-for-block basis, because a recovery operation applies changes block-for-block using the physical rowid. The database schema, including indexes, must be the same, and the database cannot be opened (other than for read-only access). If opened, the physical standby database will have different rowids, making continued recovery impossible.


Linda
"640KB ought to be enough for anybody." - Bill Gates, 1981


----- Original Message ----
From: YONGLONG_LI <oracledba-ezmlmshield-x59707836.[Email address protected]
To: LazyDBA Discussion <[Email address protected]
Sent: Thursday, February 28, 2008 11:05:59 PM
Subject: RE: RAC 10g

Dears:
Pls tell me what difference are both Physical standby and Logical
standby database.
Thanks!

-----Original Message-----
From: Menaka
[mailto:oracledba-ezmlmshield-x18955266.[Email address protected]
Sent: Friday, February 29, 2008 12:49 PM
To: LazyDBA Discussion
Subject: RAC 10g

Thanks Amar Shah

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