In sweet memories of my ever loving brother "kutty thambi " ARUN KUMAR

Friday, August 27, 2010

Transparent Application Failover TAF Demo

Transparent Application Failover TAF Demo

here, i demonstrated the demo of TAF , i concentrate only the practical demo, for theoretical part refer the oracle documentation.

1. BASIC METHOD
ADD THE ENTRIES TO THE RAC DATABASE NODE1 tnsnames.ora file
CDBS_TAF =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = racnode1-vip.localdomain)(PORT = 1521))
    (ADDRESS = (PROTOCOL = TCP)(HOST = racnode2-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@racnode1 bin]# ./crs_stat -t
Name           Type           Target    State     Host
------------------------------------------------------------
ora....s1.inst application    ONLINE    ONLINE    racnode1
ora....s2.inst application    ONLINE    ONLINE    racnode2
ora....bs1.srv application    ONLINE    ONLINE    racnode1
ora....bs2.srv application    ONLINE    ONLINE    racnode2
ora...._srv.cs application    ONLINE    ONLINE    racnode2
ora.cdbs.db    application    ONLINE    ONLINE    racnode2
ora....SM1.asm application    ONLINE    ONLINE    racnode1
ora....E1.lsnr application    ONLINE    ONLINE    racnode1
ora....de1.gsd application    ONLINE    ONLINE    racnode1
ora....de1.ons application    ONLINE    ONLINE    racnode1
ora....de1.vip application    ONLINE    ONLINE    racnode1
ora....SM2.asm application    ONLINE    ONLINE    racnode2
ora....E2.lsnr application    ONLINE    ONLINE    racnode2
ora....de2.gsd application    ONLINE    ONLINE    racnode2
ora....de2.ons application    ONLINE    ONLINE    racnode2
ora....de2.vip application    ONLINE    ONLINE    racnode2

[oracle@racnode1 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 = racnode1-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 = racnode2-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@racnode1 ~]$ sqlplus system/oracle@CDBS1_TAF

SQL*Plus: Release 10.2.0.1.0 - Production on Fri Aug 27 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


SQL>


Hope, this will helps you to understand the TAF.

for theoritical part please refer oracle documentation.

Regards,
RAJESHKUMAR G

2 comments:

Anonymous said...

Hi

This was my exam question last week and still not sure about the answer.
Any help is much appreciated.


Which three statements are true about services and transparent application failover (TAF)

A-)TAF has been configured for a service, sessions using that service fail over to a surviving instance when an outage occurs
B-)The TAF setting on a service can be none, basic, preconnect or postconnect and overrides and TAF setting in the client connection definition.
C-)TAF can restart a query after failover has completed but for other statements such as insert,update or delete, the application must resubmit the transaction
D-)The Taf setting for a client connection overrides any TAF setting in the service definition
E-)Services simplify the deployment of TAF because definining a TAF policy for a service, all connections using this service will automatically have TAF enabled

Anonymous said...

Answers are A,C,E

 
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