during flight when wx requested from Acars, sometimes a msg appears 'buffer full msg not generated', as a result required information cannot be sent. what is this msg mean,
Now where did I put that memo... .
If memory serves me correctly, the problem arises because ground stations and onboard comms systems are not co-operating, so your "outbox" is filling up. The data memories are so small on these systems that they fill up quite quickly.
On FANS-equipped 747-400, a similar problem occurs, but the memory is within the FMC, so, on the ground, you have to cycle the FMC CB's. I'm not sure where the memory is on your aircraft (could be purely an ACARS function). When we have problems specifically with ACARS, we cycle the AC and DC CBs. However, this is going to dump ALL your data. You might not want to do this in flight even though Maint Control tells you it's ok to do so.
Patience might be the only option. If you're lucky, the ground station might start responding. Anyway, when you land, get maintenance to cycle the appropriate CB's, to completely clear the memory. The CB's may have to be left out for a minute or so to do a complete dump. By the way, this is a manufacturer-approved procedure for fixing this problem.
Rgds
NSEU