Behavior when one of the instance is down

Question

Dears,
We have a reporting server(IBM Cognos BI) using Oracle RAC as the data warehouse.  Cognos uses OCI to communicate with Oracle database(Oracle client is installed with the cognos server machine). Cognos only issues SELECT statements to the database.
This is our tnsnames.ora file looks like
${DB_NAME}=
(DESCRIPTION=
  (ENABLE=BROKEN)
  (LOAD_BALANCE=off)
  (FAILOVER=on)
  (ADDRESS=(PROTOCOL=tcp)(HOST=${VIP1_IP})(PORT=11521))
  (ADDRESS=(PROTOCOL=tcp)(HOST=${VIP2_IP})(PORT=11521))
  (CONNECT_DATA=
     (SERVICE_NAME=${DB_NAME})
    (FAILOVER_MODE=(TYPE=select)(METHOD=basic))
     (server = dedicated)
As to TYPE=SELECT, it is said that if the instance on which the select statement is being executed is down, one of the available oracle instances will take over as nothing has happened. The failover is transparent to the application(Cognos). http://www.dba-oracle.com/art_oramag_rac_taf.htm
But when we manually shutdown an instance , we did not see the result as expected while get the following:
ORA-25402: transaction must roll back
Cause: A failure occured while a transaction was active on this connection.
Action: The client must roll back.
So, it looks like if application wants to take the advantage of this functionality, the application must be modified to do something related to transaction termination, Right? If so, like a product as Cognos, not a project, it could not do things specific to a particular database. 
Any suggestion is welcome.
Ricky
Thanks,

Answer 1

HI,
Please check your configuration as per below link.
http://www.oracle.com/technetwork/database/features/oci/taf-10-133239.pdf
FAST CONNECTION FAILOVER
Fast Connection Failover (FCF) is a packaged implementation of FAN included in Oracle Application Server 10g. In the event of a failure, it will act on the FAN event, clean up stale connections, and pass the notification to the application as a SQL exception. The application can then retry the connection and replay the transaction. It works with JDBC connection pools, and is not dependent on OCI or TAF. Thus, you can use FCF with both the thin JDBC driver as well as the thick (OCI) JDBC driver. Oracle does not recommend the use of both TAF and FCF with the same application.