What is the advantage of setting up TAF (Transient application failover) ?
If a node crashes, by deafault, all users will connect to available nodes.
I dont understand the benefit of using TAF (METHOD = PRECONNECT or BASIC)
Yes, I`ve already read the doc.
In the document it says: TAF is a client-side feature that allows clients to reconnect to surviving databases in the event of a failure of a database instance
Well, you dont need a TAF to connect surviving instance. If the instance is down, by default all new connection will go to surviving instances.
In absence of TAF, subsequent sessions will failover but current running sessions will not be failed over to surviving instances.
If TAF is configured with SELECT TAF policy, both session and select query will resume on a surviving instance. Any other statements (DML, PL/SQL) will not failover.
If TAF is configured with SESSION TAF policy, only session will resume on a surviving instance. query will have to be reissued.
Hope it helps!