elsie,
Depending on how your pool is plumbed, you may have a valve that controls flow from the main drain. If that's closed, you won't have any suction there. As JohnT said, your drain could also have been intentionally capped because of a plumbing leak. It could also just be plugged up with something.

Modern pool drains have anti-vortex covers that minimize the sucking force generated by the flow of water. Main drains are also installed in interconnected pairs that are placed a couple of feet apart so that, without being extremely large or extremely flexible or both, a person can't seal off the main drain and become entrapped. There's still some danger though as one of the main drains could be blocked by something (deflated pool toy comes to mind) renedering the other one a hazard to an incautious swimmer. The anti-vortex cover would still make entrapment unlikely but it's definitely possible in such a scenario. Couple one blocked main drain with a missing or old style cover on the other and you've got a tragedy waiting to happen.

I generally keep my main drain valve at the pad closed. I do that as a safety precaution and to maximize flow through the skimmers.