vash021 said:
Ask to your university or college. Normally 9 credits, no less then 3 per course, is considered full-time, but to have a better answer ask.
Also, CIC on their Glossary website (http://www.cic.gc.ca/english/helpcentre/glossary.asp#f) says:
Full-time study
Study schedule with a minimum number of hours (15 hours) of instruction per week during the academic year, including any period of training in the workplace that is part of the student's studies.
Students should ask their school what the full-time requirements are.
Full time study status
Full time study status is determined by your educational institution (school). It is usually based on the number of classroom hours per week.
The final word is from you education institution. CIC will respect the decision of your education institution if they are considered a DLI.