Data Guard Physical Standby Setup 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
contains an updated version of the 9i physical standby setup method posted here.
- Start Apply Process
- Test Log Transport
- Protection Mode
- Database Switchover
- Failover
- Flashback Database
- Read-Only Standby and Active Data Guard
- Snapshot Standby
Related
articles.
Assumptions
- You have two servers (physical or VMs) with an operating system and Oracle installed on them. In this case I've used Oracle Linux 5.6 and Oracle Database 11.2.0.2.
- The primary server has a running instance.
- The standby server has a software only installation.
Primary Server Setup
Logging
Check that
the primary database is in archivelog mode.
SELECT log_mode FROM
v$database;
LOG_MODE
------------
NOARCHIVELOG
SQL>
LOG_MODE
------------
NOARCHIVELOG
SQL>
If it is
noarchivelog mode, switch is to archivelog mode.
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE ARCHIVELOG;
ALTER DATABASE OPEN;
STARTUP MOUNT;
ALTER DATABASE ARCHIVELOG;
ALTER DATABASE OPEN;
Enabled
forced logging by issuing the following command.
ALTER DATABASE FORCE LOGGING;
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>
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. The DB_UNIQUE_NAME values of the
primary and standby database should be used in the DG_CONFIG setting of the
LOG_ARCHIVE_CONFIG parameter. For this example, the standby database will have
the value "DB11G_STBY".
ALTER SYSTEM SET
LOG_ARCHIVE_CONFIG='DG_CONFIG=(DB11G,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 an 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;
ALTER SYSTEM SET LOG_ARCHIVE_DEST_STATE_2=ENABLE;
The
LOG_ARCHIVE_FORMAT and LOG_ARCHIVE_MAX_PROCESSES parameters must be set to
appropriate values and the REMOTE_LOGIN_PASSWORDFILE must be set to exclusive.
ALTER SYSTEM SET LOG_ARCHIVE_FORMAT='%t_%s_%r.arc'
SCOPE=SPFILE;
ALTER SYSTEM SET LOG_ARCHIVE_MAX_PROCESSES=30;
ALTER SYSTEM SET REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE SCOPE=SPFILE;
ALTER SYSTEM SET LOG_ARCHIVE_MAX_PROCESSES=30;
ALTER SYSTEM SET REMOTE_LOGIN_PASSWORDFILE=EXCLUSIVE SCOPE=SPFILE;
In
addition to the previous setting, it is recommended to make sure the primary is
ready to switch roles to become a standby. For that to work properly we need to
set the following parameters. Adjust the *_CONVERT parameters to account for
your filename and patch differences between the servers.
ALTER SYSTEM SET FAL_SERVER=DB11G_STBY;
--ALTER SYSTEM SET DB_FILE_NAME_CONVERT='DB11G_STBY','DB11G' SCOPE=SPFILE;
--ALTER SYSTEM SET LOG_FILE_NAME_CONVERT='DB11G_STBY','DB11G' SCOPE=SPFILE;
ALTER SYSTEM SET STANDBY_FILE_MANAGEMENT=AUTO;
--ALTER SYSTEM SET DB_FILE_NAME_CONVERT='DB11G_STBY','DB11G' SCOPE=SPFILE;
--ALTER SYSTEM SET LOG_FILE_NAME_CONVERT='DB11G_STBY','DB11G' SCOPE=SPFILE;
ALTER SYSTEM SET STANDBY_FILE_MANAGEMENT=AUTO;
Remember,
some of the parameters are not modifiable, so the database will need to be
restarted before they take effect.
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.
DB11G =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = ol5-112-dga1)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = DB11G.WORLD)
)
)
DB11G_STBY =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = ol5-112-dga2)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = DB11G.WORLD)
)
)
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = ol5-112-dga1)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = DB11G.WORLD)
)
)
DB11G_STBY =
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = ol5-112-dga2)(PORT = 1521))
)
(CONNECT_DATA =
(SERVICE_NAME = DB11G.WORLD)
)
)
Backup Primary Database
If you are
planning to use an active duplicate to create the standby database, then this
step is unnecessary. For a backup-based duplicate, or a manual restore, take a
backup of the primary database.
$ rman target=/
RMAN> BACKUP DATABASE PLUS ARCHIVELOG;
RMAN> BACKUP DATABASE PLUS ARCHIVELOG;
Create Standby Controlfile and PFILE
Create a
controlfile for the standby database by issuing the following command on the
primary database.
ALTER DATABASE CREATE STANDBY CONTROLFILE AS
'/tmp/db11g_stby.ctl';
Create a
parameter file for the standby database.
CREATE PFILE='/tmp/initDB11G_stby.ora' FROM SPFILE;
Amend the
PFILE making the entries relevant for the standby database. I'm making a
replica of the original server, so in my case I only had to amend the following
parameters.
*.db_unique_name='DB11G_STBY'
*.fal_server='DB11G'
*.log_archive_dest_2='SERVICE=db11g ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=DB11G'
*.fal_server='DB11G'
*.log_archive_dest_2='SERVICE=db11g ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=DB11G'
Standby Server Setup (Manual)
Copy Files
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
$ mkdir -p /u01/app/oracle/fast_recovery_area/DB11G
$ mkdir -p /u01/app/oracle/admin/DB11G/adump
Copy the
files from the primary to the standby server.
$ # Standby controlfile to all locations.
$ scp oracle@ol5-112-dga1:/tmp/db11g_stby.ctl /u01/app/oracle/oradata/DB11G/control01.ctl
$ cp /u01/app/oracle/oradata/DB11G/control01.ctl /u01/app/oracle/fast_recovery_area/DB11G/control02.ctl
$ # Archivelogs and backups
$ scp -r oracle@ol5-112-dga1:/u01/app/oracle/fast_recovery_area/DB11G/archivelog /u01/app/oracle/fast_recovery_area/DB11G
$ scp -r oracle@ol5-112-dga1:/u01/app/oracle/fast_recovery_area/DB11G/backupset /u01/app/oracle/fast_recovery_area/DB11G
$ # Parameter file.
$ scp oracle@ol5-112-dga1:/tmp/initDB11G_stby.ora /tmp/initDB11G_stby.ora
$ # Remote login password file.
$ scp oracle@ol5-112-dga1:$ORACLE_HOME/dbs/orapwDB11G $ORACLE_HOME/dbs
$ scp oracle@ol5-112-dga1:/tmp/db11g_stby.ctl /u01/app/oracle/oradata/DB11G/control01.ctl
$ cp /u01/app/oracle/oradata/DB11G/control01.ctl /u01/app/oracle/fast_recovery_area/DB11G/control02.ctl
$ # Archivelogs and backups
$ scp -r oracle@ol5-112-dga1:/u01/app/oracle/fast_recovery_area/DB11G/archivelog /u01/app/oracle/fast_recovery_area/DB11G
$ scp -r oracle@ol5-112-dga1:/u01/app/oracle/fast_recovery_area/DB11G/backupset /u01/app/oracle/fast_recovery_area/DB11G
$ # Parameter file.
$ scp oracle@ol5-112-dga1:/tmp/initDB11G_stby.ora /tmp/initDB11G_stby.ora
$ # Remote login password file.
$ scp oracle@ol5-112-dga1:$ORACLE_HOME/dbs/orapwDB11G $ORACLE_HOME/dbs
Start Listener
Make sure
the listener is started on the standby server.
$ lsnrctl start
Restore Backup
Create the
SPFILE form the amended PFILE.
$ export ORACLE_SID=DB11G
$ sqlplus / as sysdba
SQL> CREATE SPFILE FROM PFILE='/tmp/initDB11G_stby.ora';
$ sqlplus / as sysdba
SQL> CREATE SPFILE FROM PFILE='/tmp/initDB11G_stby.ora';
Restore
the backup files.
$ export ORACLE_SID=DB11G
$ rman target=/
RMAN> STARTUP MOUNT;
RMAN> RESTORE DATABASE;
$ rman target=/
RMAN> STARTUP MOUNT;
RMAN> RESTORE DATABASE;
Create Redo Logs
Create
online redo logs for the standby. It's a good idea to match the configuration
of the primary server.
ALTER SYSTEM SET STANDBY_FILE_MANAGEMENT=MANUAL;
ALTER DATABASE ADD LOGFILE ('/u01/app/oracle/oradata/DB11G/online_redo01.log') SIZE 50M;
ALTER DATABASE ADD LOGFILE ('/u01/app/oracle/oradata/DB11G/online_redo02.log') SIZE 50M;
ALTER DATABASE ADD LOGFILE ('/u01/app/oracle/oradata/DB11G/online_redo03.log') SIZE 50M;
ALTER SYSTEM SET STANDBY_FILE_MANAGEMENT=AUTO;
ALTER DATABASE ADD LOGFILE ('/u01/app/oracle/oradata/DB11G/online_redo01.log') SIZE 50M;
ALTER DATABASE ADD LOGFILE ('/u01/app/oracle/oradata/DB11G/online_redo02.log') SIZE 50M;
ALTER DATABASE ADD LOGFILE ('/u01/app/oracle/oradata/DB11G/online_redo03.log') SIZE 50M;
ALTER SYSTEM SET STANDBY_FILE_MANAGEMENT=AUTO;
In
addition to the online redo logs, you should create standby redo logs on both
the standby and 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 is 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;
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;
Once this
is complete, we can start the apply process.
Standby Server Setup (DUPLICATE)
Copy Files
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
$ mkdir -p /u01/app/oracle/fast_recovery_area/DB11G
$ mkdir -p /u01/app/oracle/admin/DB11G/adump
Copy the
files from the primary to the standby server.
$ # Standby controlfile to all locations.
$ scp oracle@ol5-112-dga1:/tmp/db11g_stby.ctl /u01/app/oracle/oradata/DB11G/control01.ctl
$ cp /u01/app/oracle/oradata/DB11G/control01.ctl /u01/app/oracle/fast_recovery_area/DB11G/control02.ctl
$ # Parameter file.
$ scp oracle@ol5-112-dga1:/tmp/initDB11G_stby.ora /tmp/initDB11G_stby.ora
$ # Remote login password file.
$ scp oracle@ol5-112-dga1:$ORACLE_HOME/dbs/orapwDB11G $ORACLE_HOME/dbs
$ scp oracle@ol5-112-dga1:/tmp/db11g_stby.ctl /u01/app/oracle/oradata/DB11G/control01.ctl
$ cp /u01/app/oracle/oradata/DB11G/control01.ctl /u01/app/oracle/fast_recovery_area/DB11G/control02.ctl
$ # Parameter file.
$ scp oracle@ol5-112-dga1:/tmp/initDB11G_stby.ora /tmp/initDB11G_stby.ora
$ # Remote login password file.
$ scp oracle@ol5-112-dga1:$ORACLE_HOME/dbs/orapwDB11G $ORACLE_HOME/dbs
Start Listener
When using
active duplicate, the standby server requires static listener configuration in
a "listener.ora" file. In this case I used the following
configuration.
SID_LIST_LISTENER =
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = DB11G.WORLD)
(ORACLE_HOME = /u01/app/oracle/product/11.2.0/db_1)
(SID_NAME = DB11G)
)
)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = ol5-112-dga2.localdomain)(PORT = 1521))
)
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
)
)
ADR_BASE_LISTENER = /u01/app/oracle
(SID_LIST =
(SID_DESC =
(GLOBAL_DBNAME = DB11G.WORLD)
(ORACLE_HOME = /u01/app/oracle/product/11.2.0/db_1)
(SID_NAME = DB11G)
)
)
LISTENER =
(DESCRIPTION_LIST =
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = ol5-112-dga2.localdomain)(PORT = 1521))
)
(DESCRIPTION =
(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))
)
)
ADR_BASE_LISTENER = /u01/app/oracle
Make sure
the listener is started on the standby server.
$ lsnrctl start
Create Standby Redo Logs on Primary Server
The
DUPLICATE command automatically creates the standby redo logs on the standby.
To make sure the primary database is configured for switchover, we must create
the standby redo logs on the primary server.
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;
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;
Create Standby Using DUPLICATE
Start the
auxillary 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';
$ sqlplus / as sysdba
SQL> STARTUP NOMOUNT PFILE='/tmp/initDB11G_stby.ora';
Connect to
RMAN, specifying a full connect string for both the TARGET and AUXILLARY
instances. DO not attempt to use OS authentication.
$ rman TARGET sys/password@DB11G AUXILIARY sys/password@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'
SET LOG_ARCHIVE_DEST_2='SERVICE=db11g ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=DB11G'
SET FAL_SERVER='DB11G' COMMENT 'Is primary'
NOFILENAMECHECK;
FOR STANDBY
FROM ACTIVE DATABASE
DORECOVER
SPFILE
SET db_unique_name='DB11G_STBY' COMMENT 'Is standby'
SET LOG_ARCHIVE_DEST_2='SERVICE=db11g ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=DB11G'
SET FAL_SERVER='DB11G' COMMENT 'Is primary'
NOFILENAMECHECK;
A brief
explanation of the individual clauses is shown below.
- FOR STANDBY: This tells the DUPLICATE command is to be used for a standby, so it will not force a DBID change.
- FROM ACTIVE DATABASE: The DUPLICATE will be created directly from the source datafile, without an additional backup step.
- DORECOVER: The DUPLICATE will include the recovery step, bringing the standby up to the current point in time.
- SPFILE: Allows us to reset values in the spfile when it is copied from the source server.
- NOFILENAMECHECK: Destination file locations are not checked.
Once the
command is complete, we can start the apply process.
Start Apply Process
Start the
apply process on standby server.
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM
SESSION;
If you
need to cancel the apply process, issue the following command.
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;
If you
prefer, you can set a delay between the arrival of the archived redo log and it
being applied on the standby server using the following commands.
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DELAY 30 DISCONNECT FROM SESSION;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE NODELAY DISCONNECT FROM SESSION;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DELAY 30 DISCONNECT FROM SESSION;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE NODELAY DISCONNECT FROM SESSION;
Test Log Transport
On the
primary server, check the latest archived redo log and force a log switch.
ALTER SESSION SET nls_date_format='DD-MON-YYYY
HH24:MI:SS';
SELECT sequence#, first_time, next_time
FROM v$archived_log
ORDER BY sequence#;
ALTER SYSTEM SWITCH LOGFILE;
SELECT sequence#, first_time, next_time
FROM v$archived_log
ORDER BY sequence#;
ALTER SYSTEM SWITCH LOGFILE;
Check the
new archived redo log has arrived at the standby server and been applied.
ALTER SESSION SET nls_date_format='DD-MON-YYYY
HH24:MI:SS';
SELECT sequence#, first_time, next_time, applied
FROM v$archived_log
ORDER BY sequence#;
SELECT sequence#, first_time, next_time, applied
FROM v$archived_log
ORDER BY sequence#;
Protection Mode
There are
three protection modes for the primary database:
- Maximum Availability: Transactions on the primary do not commit until redo information has been written to the online redo log and the standby redo logs of at least one standby location. If no standby location is available, it acts in the same manner as maximum performance mode until a standby becomes available again.
- Maximum Performance: Transactions on the primary commit as soon as redo information has been written to the online redo log. Transfer of redo information to the standby server is asynchronous, so it does not impact on performance of the primary.
- Maximum Protection: Transactions on the primary do not commit until redo information has been written to the online redo log and the standby redo logs of at least one standby location. If not suitable standby location is available, the primary database shuts down.
By default
a newly created standby database is in maximum performance mode.
SELECT protection_mode FROM
v$database;
PROTECTION_MODE
--------------------
MAXIMUM PERFORMANCE
SQL>
PROTECTION_MODE
--------------------
MAXIMUM PERFORMANCE
SQL>
The mode
can be switched using the following commands. Note the alterations in the redo
transport attributes.
-- Maximum Availability.
ALTER SYSTEM SET LOG_ARCHIVE_DEST_2='SERVICE=db11g_stby AFFIRM SYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=DB11G_STBY';
ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE AVAILABILITY;
-- Maximum Performance.
ALTER SYSTEM SET LOG_ARCHIVE_DEST_2='SERVICE=db11g_stby NOAFFIRM ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=DB11G_STBY';
ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PERFORMANCE;
-- Maximum Protection.
ALTER SYSTEM SET LOG_ARCHIVE_DEST_2='SERVICE=db11g_stby AFFIRM SYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=DB11G_STBY';
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PROTECTION;
ALTER DATABASE OPEN;
ALTER SYSTEM SET LOG_ARCHIVE_DEST_2='SERVICE=db11g_stby AFFIRM SYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=DB11G_STBY';
ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE AVAILABILITY;
-- Maximum Performance.
ALTER SYSTEM SET LOG_ARCHIVE_DEST_2='SERVICE=db11g_stby NOAFFIRM ASYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=DB11G_STBY';
ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PERFORMANCE;
-- Maximum Protection.
ALTER SYSTEM SET LOG_ARCHIVE_DEST_2='SERVICE=db11g_stby AFFIRM SYNC VALID_FOR=(ONLINE_LOGFILES,PRIMARY_ROLE) DB_UNIQUE_NAME=DB11G_STBY';
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE SET STANDBY DATABASE TO MAXIMIZE PROTECTION;
ALTER DATABASE OPEN;
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
statements.
-- Convert primary database to standby
CONNECT / AS SYSDBA
ALTER DATABASE COMMIT TO SWITCHOVER TO STANDBY;
-- Shutdown primary database
SHUTDOWN IMMEDIATE;
-- Mount old primary database as standby database
STARTUP NOMOUNT;
ALTER DATABASE MOUNT STANDBY DATABASE;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;
CONNECT / AS SYSDBA
ALTER DATABASE COMMIT TO SWITCHOVER TO STANDBY;
-- Shutdown primary database
SHUTDOWN IMMEDIATE;
-- Mount old primary database as standby database
STARTUP NOMOUNT;
ALTER DATABASE MOUNT STANDBY DATABASE;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT FROM SESSION;
On the
original standby database issue the following commands.
-- Convert standby database to primary
CONNECT / AS SYSDBA
ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;
-- Shutdown standby database
SHUTDOWN IMMEDIATE;
-- Open old standby database as primary
STARTUP;
CONNECT / AS SYSDBA
ALTER DATABASE COMMIT TO SWITCHOVER TO PRIMARY;
-- Shutdown standby database
SHUTDOWN IMMEDIATE;
-- Open old standby database as primary
STARTUP;
Once this
is complete, test the log transport as before. If everything is working fine,
switch the primary database back to the original server by doing another
switchover. This is known as a switchback.
Failover
If the
primary database is not available the standby database can be activated as a
primary database using the following statements.
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE FINISH;
ALTER DATABASE ACTIVATE STANDBY DATABASE;
ALTER DATABASE ACTIVATE STANDBY DATABASE;
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 (shown
here). If not, the whole setup process must be
followed, but this time using the original primary server as the standby.
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. That process is shown
here.
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;
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;
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;
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.
If you are
using RAC, turn off all but one of the RAC instances. Make sure the instance is
in MOUNT mode.
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
STARTUP MOUNT;
Make sure
managed recovery is disabled.
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE CANCEL;
Convert
the standby to a snapshot standby. The following example queries the V$DATABASE
view to show that flashback database is not enabled prior to the conversion
operation.
SELECT flashback_on FROM
v$database;
FLASHBACK_ON
------------------
NO
ALTER DATABASE CONVERT TO SNAPSHOT STANDBY;
ALTER DATABASE OPEN;
SELECT flashback_on FROM v$database;
FLASHBACK_ON
------------------
RESTORE POINT ONLY
SQL>
FLASHBACK_ON
------------------
NO
ALTER DATABASE CONVERT TO SNAPSHOT STANDBY;
ALTER DATABASE OPEN;
SELECT flashback_on FROM v$database;
FLASHBACK_ON
------------------
RESTORE POINT ONLY
SQL>
You can
now do treat the standby like any read-write database.
To convert
it back to the physical standby, losing all the changes made since the
conversion to snapshot standby, issue the following commands.
SHUTDOWN IMMEDIATE;
STARTUP MOUNT;
ALTER DATABASE CONVERT TO PHYSICAL STANDBY;
SHUTDOWN IMMEDIATE;
STARTUP NOMOUNT;
ALTER DATABASE MOUNT STANDBY DATABASE;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT;
SELECT flashback_on FROM v$database;
FLASHBACK_ON
------------------
NO
SQL>
STARTUP MOUNT;
ALTER DATABASE CONVERT TO PHYSICAL STANDBY;
SHUTDOWN IMMEDIATE;
STARTUP NOMOUNT;
ALTER DATABASE MOUNT STANDBY DATABASE;
ALTER DATABASE RECOVER MANAGED STANDBY DATABASE DISCONNECT;
SELECT flashback_on FROM v$database;
FLASHBACK_ON
------------------
NO
SQL>
The
standby is once again in managed recovery and archivelog shipping is resumed.
Notice that flashback database is still not enabled.
For more
information see: