SQL Database vs Writing Java Serialized Objects To File?
<p>I have a web application written in java and it is about course scheduling. I used file system to store my data. I serialized my collentions (objects in them) and collect them into an serialalized object. Every user has a few file for system data and backup or prepared table data. My program is reading that file (only system data) when user entered and writing it to that file when user exit. 
Object design is very complex and there are many many-to-many relations between my objects. Writing data of this program requires so much join operation and well design schema in SQL. Furthermore a user generally have thousands of information containing hundreds of courses, teacher, rooms and even thousands of constraints. Beside of those, there is no connection between users. 
In this program I do not see any advantage of using sql. Even my system is running very fast. However lots of developers which do not know structure of my program advised to me to carry my database system to SQL.</p>

<p>What is the advantage of SQL against file system (with serialized objects) especially for my extraordinary system?</p>