session_info in v$logminer_contents

Hi ,

i query few records from v$logminer_contents .
found username and session_info values for some records and for remaining records session_info and username is blank .

could anybody explain me this behaviour ?? can we find username and session_info for other records ?

Thanks for your time

It would help to know what operations have the blank values. Some records are system generated - I think commits do not always get assigned a userid