What does it mean? What do I do about it?
The database startup parameter -prefetchDelay eliminates a network message used to send the initial record in a query before the rest of the result set.
In the 1980s the prefetch behavior made sense. The relative network and CPU speeds were such that returning the first record to the client eliminated end-user waiting. With modern systems this delay adds to overhead rather than improving performance.
You should implement -prefetchDelay in your database startup parameter file.
See also Got remote clients? Use prefetch!