RSC/MP Programming Manual

Application Development Using a Backup TDP
2. Attempt to reconnect to the TDP. Reconnection attempts should occur at
reasonable intervals for a reasonable period of time; for example, the application
should make a connection attempt every 5 seconds for 60 seconds, or longer. If
the connection cannot be established, notify the user that the application has failed
and that operator intervention is required.
3. After the connection has been re-established, begin a new session.
4. If the connection failure occurred on an RscEnd Transaction request, analyze the
database to determine if the transaction was really committed. If it was not, the
transaction was in progress at the time of the failure and was aborted.
5. If a transaction was in progress at the time of the failure, resubmit the entire
transaction.
6. Inform the user that the connection-failure recovery was completed.
See Section 7, Message Handling, for more information about handling TDP failures
and recovering from data communications failures.
Using a Backup TDP
The TDP process checkpoints configuration information; therefore, the backup TDP
process has the same configuration as the primary process. The backup process does
not save transactions or I/Os, it only saves the configuration. After a TDP failure,
applications must re-establish the connection to the workstation and perform any
outstanding transactions in the TDP again. During the recovery process the TDP is
inaccessible to applications and the RSCCOM interface.
Note. When the backup process is started and it fails, a time delay will occur before the next
backup restart attempt. Each successive time the early failure occurs the time delay will be
increased until it reaches a maximum value (approximately 30 minutes). Thus, in an extended time
period where backup restart is impossible, successive restarts will occur no more often than the
above mentioned 30 minutes. Once the backup is started and remains operational for longer than a
stable interval the restart delay will be reset.
The TDP performs these tasks during the recovery process:
Reopens the log file (if one was open at the time of the failure)
Re-establishes the operational state of all objects that were configured at the time
of primary process failure
If system resources that support these objects are no t immediately available, the
object stops or enters automatic restart mode if the AUTORESTART attribute is
configured
Logs the completion of recovery
Allows RSCCOM access
HP NonStop Remote Server Call (RSC/MP) Programming Manual — 522360-006
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