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Data Guard Physical Standby Setup Using the Data Guard Broker in Oracle Database 11g Release 2

Data Guard is the name for Oracle's standby database solution, used for disaster recovery and high availability. This article is a repeat of the manual 11gR2 Data Guard setup described here, but here the Data Guard setup and administration is performed using the Data Guard Broker.

Related articles.

Assumptions

Primary Server Setup

Logging

Check that the primary database is in archivelog mode.

SELECT log_mode FROM v$database;

LOG_MODE
------------
NOARCHIVELOG

SQL>

If it is noarchivelog mode, switch is to archivelog mode.

SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE ARCHIVELOG;
ALTER DATABASE OPEN;

Enabled forced logging by issuing the following command.

ALTER DATABASE FORCE LOGGING;
-- Make sure at leat one logfile is present.
ALTER SYSTEM SWITCH LOGFILE;

Create standby redo logs on the primary database (in case of switchovers). The standby redo logs should be at least as big as the largest online redo log and there should be one extra group per thread compared the online redo logs. In my case, the following standby redo logs must be created on both servers.

ALTER DATABASE ADD STANDBY LOGFILE ('/u01/app/oracle/oradata/db11g/standby_redo01.log') SIZE 50M;
ALTER DATABASE ADD STANDBY LOGFILE ('/u01/app/oracle/oradata/db11g/standby_redo02.log') SIZE 50M;
ALTER DATABASE ADD STANDBY LOGFILE ('/u01/app/oracle/oradata/db11g/standby_redo03.log') SIZE 50M;
ALTER DATABASE ADD STANDBY LOGFILE ('/u01/app/oracle/oradata/db11g/standby_redo04.log') SIZE 50M;

If you want to user flashback database, enable it on the primary now, so it will be enabled on the standby also. It's very useful as you will see below.

ALTER DATABASE FLASHBACK ON;

Initialization Parameters

Check the setting for the DB_NAME and DB_UNIQUE_NAME parameters. In this case they are both set to "db11g" on the primary database.

SQL> show parameter db_name

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
db_name 			     string	 db11g

SQL> show parameter db_unique_name

NAME				     TYPE	 VALUE
------------------------------------ ----------- ------------------------------
db_unique_name			     string	 db11g

SQL>

The DB_NAME of the standby database will be the same as that of the primary, but it must have a different DB_UNIQUE_NAME value. For this example, the standby database will have the value "db11g_stby".

Set suitable remote archive log destinations. In this case I'm using the fast recovery area for the local location, but you could specify a location explicitly if you prefer. Notice the SERVICE and the DB_UNIQUE_NAME for the remote location reference the standby location.

ALTER SYSTEM SET LOG_ARCHIVE_DEST_2='SERVICE=db11g_stby NOAFFIRM ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=DB11G_STBY';
ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_2=ENABLE;

Make sure the STANDBY_FILE_MANAGEMENT parameter is set.

ALTER SYSTEM SET STANDBY_FILE_MANAGEMENT=AUTO;

Service Setup

Entries for the primary and standby databases are needed in the "$ORACLE_HOME/network/admin/tnsnames.ora" files on both servers. You can create these using the Network Configuration Utility (netca) or manually. The following entries were used during this setup. Notice the use of the SID, rather than the SERVICE_NAME in the entries. This is important as the broker will need to connect to the databases when they are down, so the services will not be present.

db11g =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = ol7-112-dg1)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SID = db11g)
    )
  )

db11g_stby =
  (DESCRIPTION =
    (ADDRESS_LIST =
      (ADDRESS = (PROTOCOL = TCP)(HOST = ol7-112-dg2)(PORT = 1521))
    )
    (CONNECT_DATA =
      (SID = db11g)
    )
  )

The "$ORACLE_HOME/network/admin/listener.ora" file on the primary server contains the following configuration. Since the broker will need to connect to the database when it's down, we can't rely on auto-registration with the listener, hence the explicit entry for the database.

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = ol7-112-dg1)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
  )

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = db11g_DGMGRL)
      (ORACLE_HOME = /u01/app/oracle/product/11.2.0.4/db_1)
      (SID_NAME = db11g)
    )
  )

ADR_BASE_LISTENER = /u01/app/oracle

The "$ORACLE_HOME/network/admin/listener.ora" file on the standby server contains the following configuration.

LISTENER =
  (DESCRIPTION_LIST =
    (DESCRIPTION =
      (ADDRESS = (PROTOCOL = TCP)(HOST = ol7-112-dg2)(PORT = 1521))
      (ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
    )
  )

SID_LIST_LISTENER =
  (SID_LIST =
    (SID_DESC =
      (GLOBAL_DBNAME = db11g_stby_DGMGRL)
      (ORACLE_HOME = /u01/app/oracle/product/11.2.0.4/db_1)
      (SID_NAME = db11g)
    )
  )

ADR_BASE_LISTENER = /u01/app/oracle

Once the listener.ora changes are in place, restart the listener on both servers.

lsnrctl stop
lsnrctl start

Standby Server Setup

Prepare for Duplicate

Create a parameter file for the standby database called "/tmp/initdb11g_stby.ora" with the following contents.

*.db_name='db11g'

Create the necessary directories on the standby server.

$ mkdir -p /u01/app/oracle/oradata/db11g
$ mkdir -p /u01/app/oracle/fast_recovery_area/db11g
$ mkdir -p /u01/app/oracle/admin/db11g/adump

Create a password file, with the SYS password matching that of the primary database.

$ orapwd file=/u01/app/oracle/product/11.2.0.4/db_1/dbs/orapwdb11g password=Password1 entries=10

Create Standby Using DUPLICATE

Start the auxiliary instance on the standby server by starting it using the temporary "init.ora" file.

$ export ORACLE_SID=db11g
$ sqlplus / as sysdba

SQL> STARTUP NOMOUNT PFILE='/tmp/initdb11g_stby.ora';

Connect to RMAN, specifying a full connect string for both the TARGET and AUXILIARY instances. Do not attempt to use OS authentication.

$ rman TARGET sys/Password1@db11g AUXILIARY sys/Password1@db11g_stby

Now issue the following DUPLICATE command.

DUPLICATE TARGET DATABASE
  FOR STANDBY
  FROM ACTIVE DATABASE
  DORECOVER
  SPFILE
    SET db_unique_name='DB11G_STBY' COMMENT 'Is standby'
  NOFILENAMECHECK;

If you need to convert file locations, or alter any initialisation parameters, you can do this during the DUPLICATE using the SET command.

DUPLICATE TARGET DATABASE
  FOR STANDBY
  FROM ACTIVE DATABASE
  DORECOVER
  SPFILE
    SET db_unique_name='DB11G_STBY' COMMENT 'Is standby'
    SET db_file_name_convert='/original/directory/path1/','/new/directory/path1/','/original/directory/path2/','/new/directory/path2/'
    SET log_file_name_convert='/original/directory/path1/','/new/directory/path1/','/original/directory/path2/','/new/directory/path2/'
    SET job_queue_processes='0'
  NOFILENAMECHECK;

A brief explanation of the individual clauses is shown below.

Once the command is complete, we can start using the broker.

Enable Broker

At this point we have a primary database and a standby database, so now we need to start using the Data Guard Broker to manage them. Connect to both databases (primary and standby) and issue the following command.

ALTER SYSTEM SET dg_broker_start=true;

On the primary server, issue the following command to register the primary server with the broker.

$ dgmgrl sys/Password1@db11g
DGMGRL for Linux: Version 11.2.0.4.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.
DGMGRL> CREATE CONFIGURATION my_dg_config AS PRIMARY DATABASE IS db11g CONNECT IDENTIFIER IS db11g;
Configuration "my_dg_config" created with primary database "db11g"
DGMGRL>

Now add the standby database.

DGMGRL> ADD DATABASE db11g_stby AS CONNECT IDENTIFIER IS db11g_stby MAINTAINED AS PHYSICAL;
Database "db11g_stby" added
DGMGRL>

Now we enable the new configuration.

DGMGRL> ENABLE CONFIGURATION;
Enabled.
DGMGRL>

The following commands show how to check the configuration and status of the databases from the broker.

DGMGRL> SHOW CONFIGURATION;

Configuration - my_dg_config

  Protection Mode: MaxPerformance
  Databases:
    db11g      - Primary database
    db11g_stby - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

DGMGRL> SHOW DATABASE db11g;

Database - db11g

  Role:            PRIMARY
  Intended State:  TRANSPORT-ON
  Instance(s):
    db11g

Database Status:
SUCCESS

DGMGRL> SHOW DATABASE db11g_stby;

Database - db11g_stby

  Role:            PHYSICAL STANDBY
  Intended State:  APPLY-ON
  Transport Lag:   0 seconds (computed 0 seconds ago)
  Apply Lag:       0 seconds (computed 0 seconds ago)
  Apply Rate:      0 Byte/s
  Real Time Query: OFF
  Instance(s):
    db11g

Database Status:
SUCCESS

DGMGRL>

Database Switchover

A database can be in one of two mutually exclusive modes (primary or standby). These roles can be altered at runtime without loss of data or resetting of redo logs. This process is known as a Switchover and can be performed using the following commands. Connect to the primary database (db11g) and switchover to the standby database (db11g_stby).

$ dgmgrl sys/Password1@db11g
DGMGRL for Linux: Version 11.2.0.4.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.
DGMGRL> SWITCHOVER TO db11g_stby;
Performing switchover NOW, please wait...
Operation requires a connection to instance "db11g" on database "db11g_stby"
Connecting to instance "db11g"...
Connected.
New primary database "db11g_stby" is opening...
Operation requires startup of instance "db11g" on database "db11g"
Starting instance "db11g"...
ORACLE instance started.
Database mounted.
Switchover succeeded, new primary is "db11g_stby"
DGMGRL>

Let's switch back to the original primary. Connect to the new primary (db11g_stby) and switchover to the new standby database (db11g).

$ dgmgrl sys/Password1@db11g_stby
DGMGRL for Linux: Version 11.2.0.4.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.
DGMGRL> SWITCHOVER TO db11g;
Performing switchover NOW, please wait...
Operation requires a connection to instance "db11g" on database "db11g"
Connecting to instance "db11g"...
Connected.
New primary database "db11g" is opening...
Operation requires startup of instance "db11g" on database "db11g_stby"
Starting instance "db11g"...
ORACLE instance started.
Database mounted.
Switchover succeeded, new primary is "db11g"
DGMGRL>

Database Failover

If the primary database is not available the standby database can be activated as a primary database using the following statements. Connect to the standby database (db11g_stby) and failover.

$ dgmgrl sys/Password1@db11g_stby
DGMGRL for Linux: Version 11.2.0.4.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.
DGMGRL> FAILOVER TO db11g_stby;
Performing failover NOW, please wait...
Failover succeeded, new primary is "db11g_stby"
DGMGRL>

Since the standby database is now the primary database it should be backed up immediately.

The original primary database can now be configured as a standby. If flashback database was enabled on the primary database, then this can be done relatively easily with the following command.

DGMGRL> REINSTATE DATABASE db11g;
Reinstating database "db11g", please wait...
Operation requires shutdown of instance "db11g" on database "db11g"
Shutting down instance "db11g"...
Database closed.
Database dismounted.
ORACLE instance shut down.
Operation requires startup of instance "db11g" on database "db11g"
Starting instance "db11g"...
ORACLE instance started.
Database mounted.
Continuing to reinstate database "db11g" ...
Operation requires shutdown of instance "db11g" on database "db11g"
Shutting down instance "db11g"...
ORA-01109: database not open

Database dismounted.
ORACLE instance shut down.
Operation requires startup of instance "db11g" on database "db11g"
Starting instance "db11g"...
ORACLE instance started.
Database mounted.
Continuing to reinstate database "db11g" ...
Reinstatement of database "db11g" succeeded
DGMGRL>

If flashback database is not enabled, you would have to manually recreate db11g as a standby. The basic process is the reverse of what you did previously.

# 1) Cleanup the old instance.
sqlplus / as sysdba <<EOF
SHUTDOWN IMMEDIATE;
EXIT;
EOF
 
rm -Rf /u01/app/oracle/oradata/db11g/*
rm -Rf /u01/app/oracle/fast_recovery_area/db11g
rm -Rf /u01/app/oracle/admin/db11g
mkdir -p /u01/app/oracle/fast_recovery_area/db11g
mkdir -p /u01/app/oracle/admin/db11g/adump
rm $ORACLE_HOME/dbs/spfiledb11g.ora

export ORACLE_SID=db11g
sqlplus / as sysdba <<EOF
STARTUP NOMOUNT PFILE='/tmp/initdb11g_stby.ora';
EXIT;
EOF

# 2) Connect to RMAN.
$ rman TARGET sys/Password1@db11g_stby AUXILIARY sys/Password1@db11g

# 3) Duplicate the database.
DUPLICATE TARGET DATABASE
  FOR STANDBY
  FROM ACTIVE DATABASE
  DORECOVER
  SPFILE
    SET db_unique_name='DB11G' COMMENT 'Is standby'
  NOFILENAMECHECK;

# 4) Connect to DGMDRL on the current primary.
$ dgmgrl sys/Password1@db11g_stby

# 5) Enable the new standby.
DGMGRL> ENABLE DATABASE db11g;

Flashback Database

It was already mentioned in the previous section, but it is worth drawing your attention to Flashback Database once more. Although a switchover/switchback is safe for both the primary and standby database, a failover renders the original primary database useless for converting to a standby database. If flashback database is not enabled, the original primary must be scrapped and recreated as a standby database.

An alternative is to enable flashback database on the primary (and the standby if desired) so in the event of a failover, the primary can be flashed back to the time before the failover and quickly converted to a standby database, as shown above.

Read-Only Standby and Active Data Guard

Once a standby database is configured, it can be opened in read-only mode to allow query access. This is often used to offload reporting to the standby server, thereby freeing up resources on the primary server. When open in read-only mode, archive log shipping continues, but managed recovery is stopped, so the standby database becomes increasingly out of date until managed recovery is resumed.

To switch the standby database into read-only mode, do the following.

SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE OPEN READ ONLY;

To resume managed recovery, do the following.

SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;

In 11g, Oracle introduced the Active Data Guard feature. This allows the standby database to be open in read-only mode, but still apply redo information. This means a standby can be available for querying, yet still be up to date. There are licensing implications for this feature, but the following commands show how active data guard can be enabled.

SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE OPEN READ ONLY;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;

Since managed recovery continues with active data guard, there is no need to switch back to managed recovery from read-only mode in this case.

Snapshot Standby

Introduced in 11g, snapshot standby allows the standby database to be opened in read-write mode. When switched back into standby mode, all changes made whilst in read-write mode are lost. This is achieved using flashback database, but the standby database does not need to have flashback database explicitly enabled to take advantage of this feature, thought it works just the same if it is.

Connect to the primary (db11g) database and convert the standby database (db11g_stby) to a snapshot standby.

$ dgmgrl sys/Password1@db11g
DGMGRL for Linux: Version 11.2.0.4.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.
DGMGRL> CONVERT DATABASE db11g_stby TO SNAPSHOT STANDBY;
Converting database "db11g_stby" to a Snapshot Standby database, please wait...
Database "db11g_stby" converted successfully
DGMGRL>

When you are finished with the snapshot standby, convert it back to a standby database.

$ dgmgrl sys/Password1@db11g
DGMGRL for Linux: Version 11.2.0.4.0 - 64bit Production

Copyright (c) 2000, 2009, Oracle. All rights reserved.

Welcome to DGMGRL, type "help" for information.
Connected.
DGMGRL> CONVERT DATABASE db11g_stby TO PHYSICAL STANDBY;
Converting database "db11g_stby" to a Snapshot Standby database, please wait...
Database "db11g_stby" converted successfully
DGMGRL> CONVERT DATABASE db11g_stby TO PHYSICAL STANDBY;
Converting database "db11g_stby" to a Physical Standby database, please wait...
Operation requires shutdown of instance "db11g" on database "db11g_stby"
Shutting down instance "db11g"...
Database closed.
Database dismounted.
ORACLE instance shut down.
Operation requires startup of instance "db11g" on database "db11g_stby"
Starting instance "db11g"...
ORACLE instance started.
Database mounted.
Continuing to convert database "db11g_stby" ...
Operation requires shutdown of instance "db11g" on database "db11g_stby"
Shutting down instance "db11g"...
ORA-01109: database not open

Database dismounted.
ORACLE instance shut down.
Operation requires startup of instance "db11g" on database "db11g_stby"
Starting instance "db11g"...
ORACLE instance started.
Database mounted.
Database "db11g_stby" converted successfully
DGMGRL>

The standby is once again in managed recovery and archivelog shipping is resumed. Notice that flashback database is still not enabled.

DGMGRL> SHOW CONFIGURATION;

Configuration - my_dg_config

  Protection Mode: MaxPerformance
  Databases:
    db11g      - Primary database
    db11g_stby - Physical standby database

Fast-Start Failover: DISABLED

Configuration Status:
SUCCESS

DGMGRL>

For more information see:

Hope this helps. Regards Tim...

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