Explanation/Reference:
Explanation:
Services and Transparent Application Failover
Services simplify the deployment of Transparent Application Failover (TAF).
You can define a TAF policy for a service and all connections using this service will automatically have TAF enabled.
The TAF setting on a service can be NONE, BASIC, or PRECONNECT and overrides any TAF setting in the client connection definition.
To define a TAF policy for a service, the srvctl utility can be used as shown below:
srvctl modify service -s gl.example.com -q TRUE -P
BASIC -e SELECT -z 180 -w 5 -j LONG
Where -z is the number of retries, -w is the delay between retry attempts and -j is the connection load balancing goal.
When Oracle Net Services establishes a connection to an instance, the connection remains open until the client closes the connection, the instance is shut down, or a failure occurs. If you configure TAF for the connection, then Oracle Database moves the session to a surviving instance when an outage occurs.
TAF can restart a query after failover has completed but for other types of transactions, such as INSERT, UPDATE, or DELETE, the application must roll back the failed transaction and resubmit the transaction.
You must re-execute any session customizations, in other words, ALTER SESSION statements, after failover has occurred. However, with TAF, a connection is not moved during normal processing, even if the workload changes over time.
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Oracle 11g: RAC and Grid Infrastructure Administration Accelerated 15 - 13