Snapshot Standby (New in 11g)

                      
1.Can create from the existing Physical standby database.Physical snadby db Which should besync with primary   db.

2.It is fully updatable database can open in read write mode as well as read only mode.

3.When it open in read write mode we can create additional objects like index, views, table etc on snapshot standby database.

4.Snapshot standby can receive and archive the redo from the primary but cant apply and once it convert back to   physical standby it will start applying and can be sync with primary.

   Note:- In 10g we can open the Physical standby db in read write mode and again convert back to physical standby mode using the Flash back option.

5.In 11g no need to enable Flashback database explicitly to use a snapshot standby database as long as the     physical standby is not open in read-only mode.

6.When the physical standby database is converted , as implicit guaranteed restore point is created and     Flashback Database is enabled.

7.We can use DGMGRL or sql command to convert or back physical standby.

8.The snapshot standby can be flashed back to physical standby later point of time and to the guaranteed     restore point and automatically reapplies the archive logs files which is recieved from to primary.

9.For converting the Physical standby from snapshot standby  database should be in read write mode.

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Converting physical dg to snapshot dg using data guard Broker command
DGMGRL> convert database stand to snapshot database;

our standby database name will be 'stand'
We can verfy the snapshot standby database by

sql> select database_role from v$database; and the result will be

SNAPSHOT_STANDBY

DGMGRL>show configuration
Name;DGConfig1
Enabled :yes
Protection Mode: MaxPerformance
stand- Snapshot standby database
prim- Primary database
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Converting using the SQL command.
1. Stop the redo apply if it is active.
2. On an Oracle RAC standby database, shutdown all but one instance.
3. Ensure standby database is mounted, but not open.
4. Flash back area is configured.

SQL> alter database convert to snapshot standby;

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 Restriction on Snapshot standby
1.A snapshot standby database can not be the only standby database in a maximum protection configuration.
2.A snapshot standby datbase can not the target of a switchover or failover.
3.A snapshot standby datbase can not be a fast-start failover target

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Converting the Snapshot standby to Physical using data guard broker.

A snapshot standby database must be opened at least once in read/write mode before it can converting back to a physical snapshot database.

DGMGRL>Convert database 'standdb/ to Physical standby;
cross check the conversion using following command.
DGMGRL>show configuration
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Converting the Snapshot standby to Physical using SQL command.

If RAC database is enabled shutdown all the instance accept once instance.
Ensure that the database is mounted but not open.

SQL> alter database convert to physical standby;

restart the database physical standby
restart the redo apply process oracle will appply redos.
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