DataGuard MOS Notes

Find the below very Useful MOS Notes that could help you In Data Gaurd

Step by Step Guide on Creating Physical Standby Using RMAN DUPLICATE…FROM ACTIVE DATABASE [ID 1075908.1]
Script to Collect Data Guard Physical Standby Diagnostic Information [ID 241438.1]
How to run DBUA in silent mode? [ID 422737.1]
Bug 15927527 : ORA-1555 ON ACTIVE DATA GUARD
Rman-06571: Datafile 1 Does Not Have Recoverable Copy [ID 1336872.1]

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Osama Mustafa

Logical Standby Vs Physical Standby

What is the difference between these two Data Guard configuration , When To Use them :

Physical Standby:

1- Physical Standby Database Its exactly same As Primary Database.
2-  In Physical Data Guard The archivelog Applied directly after transfer from primary database (FTP)

Properties of Physical Standby

1- Maintain Is Easy.
2- Creation is Easy .
3- Copy Of your Primary Database ( Disaster Recovery Solution ).

Usage :

High availability solutions Or disaster recovery Solution.

Logical Standby

1 – Opposite Of standby Database , Which is not Match primary Database .
2 – This Kind Of Configuration can be Opened in Read Only Mode .
3 – can have additional materialized views and indexes added for faster performance
4 – LogMiner Techniques to transfer Archivelog.

Properties Of Logical Database :

1 – Open In Read only Mode .
2 – Sometimes its used as RollBack Solution In Upgrade ,

Usage:

1 – reporting Database to avoid overhead in primary database.
2 – Query Database .

How they Works :

Regarding to Oracle documentation  :

LNS (log-write network-server) and ARCH (archiver) processes running on the primary database select archived redo logs and send them to the standby database, where the RFS (remote file server) background process within the Oracle instance performs the task of receiving archived redo-logs originating from the primary database.

Alternatively, a supplementary mechanism may transfer the archived redo logs. On the standby database a Fetch Archive Log (FAL) client monitors for gaps in the sequence of received logs. If it finds a gap, it may invoke one or more Fetch Archive Log (FAL) servers to run on the primary database to forward the missing item(s).

Once the archived redo logs have arrived, other processes (such as an ARCH (Archiver process), an MRP (Managed Recovery Process), and/or an LSP (Logical Standby Process)) may set about applying the log contents to the standby database.

 Conclusion :

The difference between physical and logical standby is in the way the changes from the primary are applied. Both created as an exact image of the primary database. Both receive redo logs from the primary database.

 Refernce :
 Oracle DataGuard architecture 

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Osama mustafa

Check DataGaurd Role Primary/Standby

Which Database is the primary Database , Which One Is the Standby

Simple Query Will Answer this , The Scenario Like the following I have Data Guard I want to check which one Of these database are Primary Or Standby How Can I do that :

SQL > select database_role from v$database;

DATABASE_ROLE
—————-
PRIMARY

The above Output Indicate that you are Now On Primary Database, Different Output for Standby

SQL > select database_role from v$database;

DATABASE_ROLE
—————-
PHYSICAL STANDBY

There’s More than One Way
SQL> SELECT controlfile_type FROM V$database;

Output On Primary Database :

CONTROL
——–
CURRENT

On Standby :

CONTROL
——–
STANDBY

Thank you
Osama Mustafa