[syslog-ng]Which signal does reload sends ?

Hi all Can you please tell me what happens when syslog-ng reloads (i.e. receives HUP signal) ? I need to know what signal does it send to the destination programs, and is it a good practice to catch this signal. In fact I don't want my destination program to die at reload, or at least I want to serialize his data structures before it dies, in order to retrieve it when it goes back. On the other hand, if a message arrives from an UDP source while syslog-ng is reloading, will it be lost ? Why the keep alive option is only for tcp source ? Thanks a lot for any help Ali