I've installed OSQA, please refer through the below link
I want to know which database file it is using??? How can i take a backup?? or is it possible to move database files to mysql database???
OSQA is configured using PostgreSQL which is the best because it supports full text searching. Take a look at http://wiki.osqa.net/display/docs/RHEL,+CentOS+5+Installation+Guide#RHEL%2CCentOS5InstallationGuide-UsingPostgreSQL. You can use MySQL database but you can not use this feature.