dba_hist_sqlstat near all column null when column FLAG = 3

Hi,

I analyse the activity on my server.

for this I use the table dba_hist_sqlstat, to search query consumption (cpu, io, gets, ..).

but  during 78 hours, some query have  all column to null except   snap_id, db_id, instance_number, sql_id , sharable_mem, version count , parse_calls_delta,cpu_time_delta, elapsed_time_delta,

plan_hash_ value is to 0 ,

undocumented FLAG column =3

somebody have any idea why when flag =3 I have no data ?