Events can be output as full event data structures or as single ZDAB banks (see section 13.6). This can be controlled on a stream by stream basis e.g.:-
file out 1 big_file.dat format=$full_ds
file out 2 tiny_file.dat format=$zdab_only
The default is taken from the TEIO bank and can be set by symbolic command e.g.:-
$default_output_option $full_ds