Failover And Recovery; Router Failover; Recovery Scenarios - Compaq Reliable Transaction Router Getting Started

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.
3–2 Reliability Features