How to store voice messages in a folder instead of database

Hi to all,
Hope you all will be fine.I am new to asterisk .I have a question that if i want that my asterisk store all voice messages to folder in my case it will be (/var/spool/asterisk/voicemail/brights/220/INBOX/) and not in the database. Right now what happen that when i record a message for extension 220 it goes to 220 INBOX folder as mentioned above but after sometime it remove from the folder and goes to database. I want that the message remain in the folder and not going to database . How can i do this please help me.

Thanks in advance