Compaq Reliable Transaction Router manual Failover and Recovery, Recovery Scenarios

Failover and Recovery

Failover and Recovery

	RTR provides several capabilities to ensure failover and recovery
	under several circumstances.
Router Failover	Frontend nodes automatically connect to another router if the
	one being used fails. This reconnection is transparent to the
	application.
	Routers are responsible for coordinating the two-phase commit
	for transactions. If the original router coordinating a transaction
	fails, backend nodes select another router that can ensure correct
	transaction completion.
Backend	Transactions in the process of being committed at the time of a
Restart	failure are recovered from RTR's disk journal. Recovery could be
Recovery	with a concurrent server, a standby server, or a restarted server
	created when the failed backend restarts.
	Correct ordering of the execution of transactions against the
	database is maintained.
Transaction	Transaction messages which are lost in transit are re-sent when
Message	possible. The frontend and backend nodes keep an in-memory
Replay	copy of all active messages for this purpose.
Link Failure	In the event of a communications failure, RTR tries to reconnect
Recovery	the link or links until it succeeds.

Recovery Scenarios

This section describes how RTR recovers from different hardware and software failure. For additional information on failure and recovery scenarios, see the RTR Application Design Guide.

3–2Reliability Features