13.3.1 About Transparent Application Failover

Transparent Application Failover enables a client to automatically reconnect to a database instance if the current instance to which the connection is made fails. Notifications are used by the server to trigger TAF callbacks on the client-side.

You can configure TAF using server-side service attributes. This is the preferred method. Alternatively, you can configure TAF in the application connect string. The server-side service attributes take precedence over the values specified in the connect string.

TAF operates in one of the following modes:

  • Session Failover: Re-creates lost connections and sessions.

  • Select Failover: Replays in-progress queries.

When there is a failure, callback functions are initiated on the client-side using Oracle Call Interface (OCI) callbacks. This works with standard OCI connections as well as connection pool and session pool connections.

TAF operates with Oracle Data Guard to provide automatic failover. TAF works with the following database configurations to effectively mask a database failure:

  • Oracle Real Application Clusters

  • Replicated systems

  • Standby databases

  • Single instance Oracle database

Related Topics

Parent topic: Configuring Transparent Application Failover