a query ...

Hello .... 

I'm new to postgresql and have recently installed it .A small thing about it is bothering me. If i dont use postgresql for some time
the database automatically shuts down. Is this a feature , a problem or a bug ??? .
 If it's a feature please tell me whether this feature is customizable and how to disable it. If its a problem then please tell me how to 
solve it and if it's a bug then please tell me a workaround ...

Thanking you in anticipation !!

regards 
abhay

p.s. :- if you can ... please mail me the solution at abhay@usindia.com  as early as possible because our deadline is nearby.