dnp3 zeek script delete dnp3_control object

[biswajitutil]

Hi,
I have a doubt regarding the zeek script where you have deleted dnp3_control if it is not originated.
However, I want to use connection information (c) when connection will be removed i.e. connection_state_remove(). So, I just want to know what these two below code snippets are doing in each event because I am expecting connection structure will stay the same till connection is removed.
1.
if ( ! c?$dnp3_control ) c$dnp3_control = [$ts=network_time(), $uid=c$uid, $id=c$id];
2.
if ( !is_orig ){ delete c$dnp3_control; }
Thanks
Biswa