In order not to fall into a long running loop, you can configure the trigger so that Deliver until is set to Max attempts reached instead of Successful. Then, set Max attempts to the number of times you want the document to be retried.
If the service being executed by the trigger is configured properly for auditing, you could then use the Monitor to resubmit the failed acks.
Another option for reprocessing the failed document(s): starting with IS 6.1 SP2, you can set the Retry failure behavior of the trigger to Suspend and retry later. This means that once the document is retried Max attempts, the trigger will actually be suspended. Once the database is back up, you can then resume the trigger to process the documents where it had left off.
You can resume the trigger manually via the Trigger Management page of the Administrator console or by executing the resume services in WmPublic/pub.trigger; OR you could set up a Resource monitoring service to do it automatically (although one could argue that using a monitoring service is not a whole lot different than the long running loop you were trying to avoid to begin with).
#Adapters-and-E-Standards#Integration-Server-and-ESB#webMethods