To set up full text search parameter minimum word length edit your main MySQL configuration file /etc/my.cnf.
In section
[mysqld]
# set minimum word length for full text search
ft_min_word_len=3
Restart MySQL using command:
# /etc/init.d/mysqld restart
Documentation: http://dev.mysql.com/doc/refman/5.0/en/fulltext-search.html
