Compaq Reliable Transaction Router - Manual (Page 46)

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
Restart
Recovery Transactions in the process of being committed at the time of a
failure are recovered from RTR’s disk journal. Recovery could be
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
Message
Replay Transaction messages which are lost in transit are re-sent when
possible. The frontend and backend nodes keep an in-memory
copy of all active messages for this purpose.
Link Failure
Recovery In the event of a communications failure, RTR tries to reconnect
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