In DataGuard Broker, this process is very
simple, you just type a few commands, re-start your DB and you are ready to
test this amazing feature!!!
What Happens in Snapshot Standby
Mode ??
The Redo data will continue to be received by
the database while it is operating as a snapshot standby database, but it will
not be applied until the snapshot standby is converted back into a physical
standby database.
Note : The Flashback Database feature
is required to create a snapshot standby database.
If Flashback database is disabled, it is
automatically enabled during conversion to a snapshot standby database.
The Snapshot Standby database in turn uses
the Flashback Database technology to create a guaranteed restore point to which
the database can be later flashed back to.
So we need to keep in mind that whatever
limitations are present in the Flashback database technology, the same will
also be inherent in the Snapshot database feature.
The broker automatically restarts the
database to the mounted state if it had been opened with Flashback Database
disabled. No user action is required.
Step 1- Connect to DG Broker
$ dgmgrl
DGMGRL> connect sys
DGMGRL> show configuration
Step 2- Convert the DB.
After the conversion takes place, internally
a guaranteed restore point has been created and the database has been opened in
read-write mode
DGMGRL> convert database 'STDBY' to snapshot standby;
Step 3- Verify that the database was
successfully converted by issuing the
SHOW CONFIGURATION command:
DGMGRL> show configuration
Configuration - prod_dg
Protection Mode: MaxPerformance
Databases:
PROD - Primary database
STDBY – Snapshot standby database
Fast-Start Failover: DISABLED
Configuration
Status: SUCCESS
Now Let’s
see,
How to
Convert Snapshot Standby back to Physical Standby with DGMGRL
The Redo data received while the database was a snapshot standby
database will be automatically applied when Redo Apply is started.
Note:
A snapshot standby database must be opened at least once
in read-write mode before it can be converted into a physical standby
database.
Step 1- Connect to DG Broker.
You should
be on the primary server to complete this step.
$ dgmgrl
DGMGRL > connect sys
Step 2- Convert the DB back to physical
DGMGRL > convert database 'stdby' to physical standby;
Step 3- Verify the
status, that the database was successfully converted by issuing the SHOW
CONFIGURATION command:
DGMGRL> show configuration
Configuration - prod_dg
Protection Mode: MaxPerformance
Databases:
PROD - Primary database
STDBY – Physical standby database
Fast-Start Failover: DISABLED
Configuration Status: SUCCESS
NOTE:
You may get the following
message during the conversion process:
“Converting database
"stdby" to a Physical Standby database, please wait...
Operation requires shutdown of
instance "STDBY" on database "stdby"
Shutting down instance
"STDBY"...
Database closed.
Database dismounted.
ORACLE instance shut down.
Operation requires startup of
instance "STDBY" on database "stdby"
Starting instance
"STDBY"...
Unable to connect to database
ORA-12514: TNS:listener does
not currently know of service requested in connect descriptor
Failed.
Warning: You are no longer
connected to ORACLE.
Please complete the following
steps and reissue the CONVERT command:
start up and mount instance
"STDBY" of database "stdby“
If so,
then connect to the STDBY and startup and mount the instance:
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