DCPP = Pension (Defined Contribution Pension Plan), therefore, 退休的时候才能取. When you are in financial difficulties, you can apply to release some fund in DCPP.
Company usually give matching to DCPP, therefore it is better than RRSP. I would max out DCPP before contribute anything to RRSP. Of course, the draw back is you have NO access to money until you are retired.