Freeradius + exec module

[Leandro]

Hi guys , I would like to run some external script after inserting new 
accounting data on my mysql database.
So far radius + mysql + accounting is already working.
So , Im looking some documentation about exec module now but I would 
like to ask:
Can anyone point some doc ?
Can the external script delay the radius daemon process or does it run 
on different thread ?

Regards ;
Leandro.