Transparent Application Failover TAF

1. BASIC METHOD
ADD THE ENTRIES TO THE RAC DATABASE NODE1 tnsnames.ora file
CDBS_TAF =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = node1-vip.localdomain)(PORT = 1521))
    (ADDRESS = (PROTOCOL = TCP)(HOST = node2-vip.localdomain)(PORT = 1521))
    (LOAD_BALANCE = yes)
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = cdbs)
      (FAILOVER_MODE=
      (TYPE=SELECT)
      (METHOD=BASIC)
     )
    )
  )
Make sure all the resources are up and running.
root@node1 bin]# ./crs_stat -t
Name           Type           Target    State     Host
------------------------------------------------------------
ora....s1.inst application    ONLINE    ONLINE    node1
ora....s2.inst application    ONLINE    ONLINE   node2
ora....bs1.srv application    ONLINE    ONLINE    node1
ora....bs2.srv application    ONLINE    ONLINE   node2
ora...._srv.cs application    ONLINE    ONLINE   node2
ora.cdbs.db    application    ONLINE    ONLINE   node2
ora....SM1.asm application    ONLINE    ONLINE    node1
ora....E1.lsnr application    ONLINE    ONLINE    node1
ora....de1.gsd application    ONLINE    ONLINE    node1
ora....de1.ons application    ONLINE    ONLINE    node1
ora....de1.vip application    ONLINE    ONLINE    node1
ora....SM2.asm application    ONLINE    ONLINE   node2
ora....E2.lsnr application    ONLINE    ONLINE   node2
ora....de2.gsd application    ONLINE    ONLINE   node2
ora....de2.ons application    ONLINE    ONLINE   node2
ora....de2.vip application    ONLINE    ONLINE   node2
[oracle@node1 admin]$ sqlplus system/oracle@CDBS_TAF
SQL*Plus: Release 10.2.0.1.0 - Production on Thu Aug 26 17:36:45 2010
Copyright (c) 1982, 2005, Oracle.  All rights reserved.

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, Real Application Clusters, OLAP and Data Mining options
SQL> show user;
USER is "SYSTEM"
SQL> col osuser format a10
SQL> col username format a10
SQL> col failover_type format a15
SQL> col failover_method format a18
SQL> select username,osuser,failover_method,failover_type from v$session
  2  where username='SYSTEM';
USERNAME   OSUSER     FAILOVER_METHOD    FAILOVER_TYPE
---------- ---------- ------------------ ---------------
SYSTEM     oracle     BASIC              SELECT

SQL> select instance_name from v$instance;
INSTANCE_NAME
----------------
cdbs1
SQL> select count(*) from demotb;
  COUNT(*)
----------
       954
SQL> select * from demotb;
run the long running query

simultaneously open another terminal and give shutdown abort instance cdbs1
SQL> shu abort
ORACLE instance shut down.
but the query runs smoothly without any interruption after the completion of the query, verify the instance name
SQL>select instance_name from v$instance;
INSTANCE_NAME
----------------
cdbs2
automatically it switch over to the instance cdbs2 , because of this user can access the database and no failure in queries. users can access without interruption.
USER will not receive any error message while running query.
2. PRECONNECT METHOD
Add the entries to the tnsnames.ora file on both nodes.
CDBS1_TAF =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = node1-vip.localdomain)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = cdbs)
      (INSTANCE_NAME = cdbs1)
      (FAILOVER_MODE=
      (BACKUP=CDBS2_TAF)
      (TYPE=SELECT)
      (METHOD=PRECONNECT)
     )
    )
  )

CDBS2_TAF =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = node2-vip.localdomain)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = cdbs)
      (INSTANCE_NAME = cdbs2)
      (FAILOVER_MODE=
      (BACKUP=CDBS1_TAF)
      (TYPE=SELECT)
      (METHOD=PRECONNECT)
     )
    )
  )
connect to the database on node1
[oracle@node1 ~]$ sqlplus system/oracle@CDBS1_TAF
SQL*Plus: Release 10.2.0.1.0 - Production on Fri June 16 12:23:11 2010
Copyright (c) 1982, 2005, Oracle.  All rights reserved.

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production
With the Partitioning, Real Application Clusters, OLAP and Data Mining options
SQL> SELECT INSTANCE_NAME FROM V$INSTANCE;
INSTANCE_NAME
----------------
cdbs1
SQL> COL USERNAME FOR a10
SQL> col osuser for a10
SQL> col failover_type format a15
SQL> col failover_method for a18
SQL> select username,failover_type,failover_method from v$session
  2  where username='SYSTEM';
USERNAME   FAILOVER_TYPE   FAILOVER_METHOD
---------- --------------- ------------------
SYSTEM     SELECT          PRECONNECT
SQL> select count(*) from demo;
  COUNT(*)
----------
     49783
run the long running query.
SQL> select * from demo;
simultaneously issue shutdown abort in new terminal
SQL> shu abort;
ORACLE instance shut down.
SQL>
the query runs smoothly, user will not receive any kind of error messages.
then check the instance name in node1 machine.
SQL> select instance_name from v$instance;
INSTANCE_NAME
----------------
cdbs2
SQL> select username,osuser,failover_type,failover_method from v$session
  2  where username='SYSTEM';
USERNAME   OSUSER     FAILOVER_TYPE   FAILOVER_METHOD
---------- ---------- --------------- ------------------
SYSTEM     oracle     SELECT          PRECONNECT
SQL>
checking node2 machine before and after TAF.
Before TAF
SQL> select username,osuser,failover_type,failover_method from v$session
  2  where username='SYSTEM';
USERNAME                       OSUSER                         FAILOVER_TYPE
------------------------------ ------------------------------ -------------
FAILOVER_M
----------
SYSTEM                         oracle                         NONE
NONE

SQL> select instance_name from v$instance;
INSTANCE_NAME
----------------
cdbs2
SQL> select instance_name from v$instance;
INSTANCE_NAME
----------------
cdbs2
After TAF.
SQL> select username,osuser,failover_type,failover_method from v$session
  2  where username='SYSTEM';
USERNAME                       OSUSER                         FAILOVER_TYPE
------------------------------ ------------------------------ -------------
FAILOVER_M
----------
SYSTEM                         oracle                         SELECT
PRECONNECT