Oracle 11gR2 - Data Guard Broker
In earlier versions of Oracle, the Data Guard Broker has been regarded with suspicion. However, in Oracle 11gR2 the Data Guard Broker is much more stable and has become the preferred tool for managing Data Guard configurations.
Given a solid foundation, implementing the Broker is almost trivial.
This page assumes that the db_name is PROD and that the db_unique_names are PROD and STBY. These names follow my customers existing standards; where possible I prefer to use geographic names for the DB_UNIQUE_NAME parameter as I think it is easier to visualize the configuration during role management.
Configure LISTENER.ORA
First, on each node add a static entry to the LISTENER.ORA file. For example:
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = PROD_DGMGRL)
(ORACLE_HOME= /u01/app/oracle/product/11.2.0/dbhome_1)
(SID_NAME = PROD)
)
)
The Data Guard Broker defaults to static service names with the DGMGRL suffix. It is possible to override the default service names, but in this case I chose the lazy option and stuck with the Oracle defaults.
Note that in a RAC environment the SID_NAME will be different on each node, so don't copy the listener.ora file between nodes.
Configure TNSNAMES.ORA
We also specified entries for both the primary and standby databases in $ORACLE_HOME/network/admin/tnsnames.ora. For example:
PROD =
(DESCRIPTION =
(ADDRESS = (PROTOCOL=TCP)(HOST=server14.juliandyke.com)(PORT=1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = PROD)
)
)
STBY =
(DESCRIPTION =
(ADDRESS = (PROTOCOL=TCP)(HOST=server15.juliandyke.com)(PORT=1521))
(CONNECT_DATA =
(SERVER = DEDICATED)
(SERVICE_NAME = STBY)
)
)
In this example, the PROD database will run on server14 and the STBY database will run on server15.
Enable Data Guard Broker
Next enable the Data Guard Broker for each database (primary and standby) in the configuration by setting the DG_BROKER_START parameter to TRUE.
ALTER SYSTEM SET dg_broker_start = TRUE;
The Data Guard Broker maintains two copies of its configurations. The locations of these files are specified by the DG_BROKER_CONFIG_FILE1 and DG_BROKER_CONFIG_FILE2 parameters. For a single instance database, the default values are:
$ORACLE_HOME/dbs/dr1<db_unique_name>.dat
$ORACLE_HOME/dbs/dr2<db_unique_name>.dat
The default values are probably adequate for a single instance database; in a RAC environment the defaults should be modified to specify a location in a shared file system or ASM diskgroup(s).
Start DGMGRL
On any node in the configuration, start the Data Guard Broker command utility (DGMGRL) and connect as the SYS user.
[oracle@server14]$ dgmgrl
DGMGRL> CONNECT SYS
Password: <Enter Password>
Note that it is not necessary to specify the SYSDBA privilege as this is assumed by DGMGRL.
Create Data Guard Broker Configuration
Create a configuration. For example:
DGMGRL> CREATE CONFIGURATION DG1' AS
> PRIMARY DATABASE IS 'PROD'
> CONNECT IDENTIFIER IS 'PROD';
Configuration "DG1" created with primary database "PROD"
You will need to specify a configuration name and the unique name of the primary database
Add standby database(s)
Add all standby databases to the configuration. In this example we just have one physical standby database:
DGMGRL> ADD DATABASE 'STBY' AS
> CONNECT IDENTIFIER IS 'STBY';
Database 'STBY' added
Enable the configuration
By default the Data Guard configuration is disabled. Enable the configuration as follows:
DGMGRL> ENABLE CONFIGURATION\nEnabled.
Switchover to standby
As we started with a working Data Guard configuration, it should be possible to switchover to the standby database at this stage. Switchover is achieved using a single command e.g.:
DGMGRL> SWITCHOVER TO 'STBY'
Performing switchover NOW, please wait...
New primary database "STBY" is opening...
Operation requires shutdown of instance "PROD" on database "PROD"
Shutting down instance "PROD"...
ORACLE instance shut down.\nOperation requires startup of instance "PROD" on database "PROD"
Starting instance "PROD"...
ORACLE instance started.
Database mounted.
Switchover succeeded, new primary is "STBY"
If the environment has been correctly configured then switchover generally works first time. However, it can take a few minutes to complete the switchover operation. If the operation does not complete immediately then don't panic. Wait for a few minutes and then check the status again.
Switchback
Switchback is very similar to switchover.
DGMGRL> SWITCHOVER TO 'PROD'
Performing switchover NOW, please wait...
New primary database "PROD" is opening...
Operation requires shutdown of instance "STBY" on database "STBY"
Shutting down instance "STBY"...
ORACLE instance shut down.
Operation requires startup of instance "STBY" on database "STBY"
Starting instance "STBY"...
ORACLE instance started.
Database mounted.
Switchover succeeded, new primary is "PROD"
As with switchover we have seen occasional failures with switchback which again we think are timing-related.
Disabling Configuration
The configuration can be disabled at any time using:
DGMGRL> DISABLE CONFIGURATION
Disabled.
Removing the configuration
The configuration can be removed using:
DGMGRL> REMOVE CONFIGURATION
Removed configuration
Checking the Data Guard Configuration
You can check the Data Guard configuration in DGMGRL using the SHOW CONFIGURATION command which has both default and verbose modes. For example:
DGMGRL> SHOW CONFIGURATION
Configuration - DG1
Protection Mode: MaxAvailability
Databases:
PROD - Primary database
STBY - Physical standby database
Fast-Start Failover: DISABLED
Configuration Status:
SUCCESS
The verbose option includes some additional properties:
DGMGRL> SHOW CONFIGURATION VERBOSE
Configuration - DG1
Protection Mode: MaxAvailability\n
Databases:
PROD - Primary database
STBY - Physical standby database
Properties:
FastStartFailoverThreshold = '30'
OperationTimeout = '30'
FastStartFailoverLagLimit = '30'
CommunicationTimeout = '180'
FastStartFailoverAutoReinstate = 'TRUE'
FastStartFailoverPmyShutdown = 'TRUE'
BystandersFollowRoleChange = 'ALL'
Fast-Start Failover: DISABLED
Configuration Status:
SUCCESS
Checking the Primary Database Configuration
The primary database configuration can be checked using the SHOW DATABASE command. This command also has a default and verbose mode:
DGMGRL> SHOW DATABASE 'PROD'
Database - PROD
Role: PRIMARY
Intended State: TRANSPORT-ON
Instance(s):
PROD
Database Status:
SUCCESS
The verbose mode includes properties for the database, many of which reflect the underlying initialization parameters:
DGMGRL> SHOW DATABASE VERBOSE 'PROD'
Database - PROD
Role: PRIMARY
Intended State: TRANSPORT-ON
Instance(s):
PROD
Properties:
DGConnectIdentifier = 'PROD'
ObserverConnectIdentifier = ''
LogXptMode = 'SYNC'
DelayMins = '0'
Binding = 'OPTIONAL'
MaxFailure = '0'
MaxConnections = '1'
ReopenSecs = '300'
NetTimeout = '30'
RedoCompression = 'DISABLE'
LogShipping = 'ON'
PreferredApplyInstance = ''
ApplyInstanceTimeout = '0'
ApplyParallel = 'AUTO'
StandbyFileManagement = 'AUTO'
ArchiveLagTarget = '0'
LogArchiveMaxProcesses = '5'
LogArchiveMinSucceedDest = '1'
DbFileNameConvert = '+DATA2, +DATA1'
LogFileNameConvert = '+FRA2, +FRA1'
FastStartFailoverTarget = ''
InconsistentProperties = '(monitor)'
InconsistentLogXptProps = '(monitor)'
SendQEntries = '(monitor)'
RecvQEntries = '(monitor)'
SidName = 'PROD'
StaticConnectIdentifier =
'(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=10.227.27.1)
(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=PROD_DGMGRL)
(INSTANCE_NAME=PROD)(SERVER=DEDICATED)))'
StandbyArchiveLocation = '+FRA1'
AlternateLocation = ''
LogArchiveTrace = '0'
LogArchiveFormat = '%t_%s_%r.dbf'
TopWaitEvents = '(monitor)'
Database Status:
SUCCESS
Checking the Physical Standby Database Configuration
The physical standby database configuration can also be checked using the SHOW DATABASE command. Again this command has a default and verbose mode:
DGMGRL> SHOW DATABASE 'STBY'
Database - STBY
Role: PHYSICAL STANDBY
Intended State:
APPLY-ON
Transport Lag: 0 seconds
Apply Lag: 0 seconds
Real Time Query: OFF
Instance(s):
STBY
Database Status:
SUCCESS
I can never remember the names of the Data Guard dynamic performance views so I really like the Transport Lag and Apply Lag fields in the above output.
Again the verbose mode includes properties for the standby database:
DGMGRL> SHOW DATABASE VERBOSE 'STBY'
Database - STBY
Role: PHYSICAL STANDBY
Intended State: APPLY-ON
Transport Lag: 0 seconds
Apply Lag: 0 seconds
Real Time Query: OFF
Instance(s):
STBY
Properties:
DGConnectIdentifier = 'STBY'
ObserverConnectIdentifier = ''
LogXptMode = 'SYNC'
DelayMins = '0'
Binding = 'OPTIONAL'
MaxFailure = '0'
MaxConnections = '1'
ReopenSecs = '300'
NetTimeout = '30'
RedoCompression = 'DISABLE'
LogShipping = 'ON'
PreferredApplyInstance = ''
ApplyInstanceTimeout = '0'
ApplyParallel = 'AUTO'
StandbyFileManagement = 'AUTO'
ArchiveLagTarget = '0'
LogArchiveMaxProcesses = '5'
LogArchiveMinSucceedDest = '1'
DbFileNameConvert = '+DATA1, +DATA2'
LogFileNameConvert = '+FRA1, +FRA2'
FastStartFailoverTarget = ''
InconsistentProperties = '(monitor)'
InconsistentLogXptProps = '(monitor)'
SendQEntries = '(monitor)'
RecvQEntries = '(monitor)'
SidName = 'PROD'
StaticConnectIdentifier =
'(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=10.221.27.2)
(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=STBY_DGMGRL)
(INSTANCE_NAME=STBY)(SERVER=DEDICATED)))'\n
StandbyArchiveLocation = '+FRA2'
AlternateLocation = ''
LogArchiveTrace = '0'
LogArchiveFormat = '%t_%s_%r.dbf'
TopWaitEvents = '(monitor)'
Database Status:
SUCCESS
