Ejabberd with MySQL

I have installed ejabberd and successfully configured it with MySQL. I can get to the administration webinterface , create users , and chat . I only have a problem with the line,

{odbc-start_interval, 30}.

It causes an error and when I commented the line out , everything works well . My questions are
1) What role does this line play ?
2) Is it ok if I leave it out ?

Thank you in advance ,

RawRoRo .