Thank you for your suggestion. Yes, in part. I have done so (from scratch) on the most relevant tables involved with this query but I cannot absolutely rule out some index corruption somewhere just yet.

There is still the unexplained issue of, at the moment, there being no slowdown problem until the second user of the morning opens the .DBC's tables. I remember something like this once happening to us. It turned out to have to do with a view and its tables' tags. View changes, here, don't seem to explain this observation.

My manager, however, has directed me to make a copy of the responsive "development" .DBC, zap its tables, import the "production" data, and then see whether we still get the normal "rapid" queries. If the delay does not appear I imagine he'll want us to simply go with this as our solution.

Thank you again for your kind help,

Spencer