DSA90804A RJDJ Measurements using SCPI & python

Hi, 

I'm extremely new on this so please bare with me. I'm trying to read Jitter measurements using the DSO90804A Oscilloscope through python and scpi commands. One problem I'm running into is that when the scope is running, the measurements are constantly being refreshed. Sometimes the scope is unable to get a good reading and it shows an "Incomplete" or 9.99E+37, which is a non-valid measurement. Is there a scpi command I can use to check whether the scope is measuring valid numbers so I can query the data at that time. Otherwise, If I query the scope three times, most of the times my results are non-valid and only once or twice do I get valid numbers.

Any help will be highly appreciated.

Thanks.

p.s. I've attached a scope shot of the issue I'm talking about. Sometimes, instead of a valid number I get an incomplete. These data refresh is very asynchronous so if I query the data I will get invalid data.