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Thread: Transparent Application Failover (TAF) setup and testing - Oracle 10g RAC

  1. #1
    Oracle Administrator
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    Feb 2012
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    New Delhi, India
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    Transparent Application Failover (TAF) setup and testing - Oracle 10g RAC

    After you have 2 or 3 nodes of Oracle 10g RAC up and running, you need to setup Transparent Application Failover (TAF) so that when one of you RAC node is down the application connections stay connected to the running nodes.

    Setup a new service called "appcon", by running dbca
    At Welcome, select "Oracle Real Application Cluster database", click Next
    Select "Service Management", click Next
    Select your RACDB databse, click Next
    Click Add and enter service name: appcon
    Select Preferred instance "RACDB3" and check the rest as Available
    Select TAF Policy: BASIC
    Click Finish
    Add "appcon" to your tnsnames.ora file

    appcon =
    (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = rac1-vip.domain.com)(PORT = 1521))
    (ADDRESS = (PROTOCOL = TCP)(HOST = rac2-vip.domain.com)(PORT = 1521))
    (ADDRESS = (PROTOCOL = TCP)(HOST = rac3-vip.domain.com)(PORT = 1521))
    (LOAD_BALANCE = yes)
    (FAILOVER = true)
    (CONNECT_DATA =
    (SERVER = DEDICATED)
    (SERVICE_NAME = appcon)
    (FAILOVER_MODE =
    (TYPE = SELECT)
    (METHOD = BASIC)
    (RETRIES = 20)
    (DELAY = 5)
    )
    )
    )

    Test connection:

    $ sqlplus system/manager@appcon

    select instance_number,instance_name,host_name from v$instance;

    INSTANCE_NUMBER INSTANCE_NAME HOST_NAME
    --------------- ---------------- -------------------------------------
    1 RACDB3 rac3.domain.com

    select failover_type,failover_method,failed_over from v$session where username='SYSTEM';

    FAILOVER_TYPE FAILOVER_M FAI
    ------------- ---------- ---
    SELECT BASIC YES

    Now try shutdown RACDB3 instance:

    $ srvctl stop instance -d RACDB -i RACDB3

    select instance_number,instance_name,host_name from v$instance;

    INSTANCE_NUMBER INSTANCE_NAME HOST_NAME
    --------------- ---------------- -------------------------------------
    1 RACDB1 rac1.domain.com

    After you restarted the database instance RACDB3, the service does not automatically relocate to the preferred database instance. You have to manually relocate the service back on RACDB3:

    $ srvctl start instance -d RACDB -i RACDB3
    $ srvctl relocate service -d RACDB -s appcon -i RACDB1 -t RACDB3

    Your sqlplus connection stays connected to the instance RACDB1 and you have reconnect. Then it will connect to the preferred instance again. Now check the service names on each database instance to see which one is the preferred instance:

    SQL> show parameters service_name

    NAME TYPE VALUE
    ------------------------------------ ----------- ------------------------------
    service_names string appcon, RACDB

  2. #2
    Expert Oracle Administrator
    Join Date
    Oct 2011
    Posts
    120
    A very good post on TAF

    Thanks

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