The 11g OCM is unlike any of the other exams. It is a 2-day hands-on lab-based exercise. You are given an Oracle server and must perform various tasks, solve problems, etc.
The OCM exam is only given at a relatively small number of times throughout the year. Strictly speaking, there are a lot of times, but they are spread throughout the world, so the number of times at a location anywhere close to you will be small -- maybe only one or two a year.
In addition to passing the exam, you must also take two hands-on courses acceptable to Oracle. You can find specific details, including the price in your area by reading and following the links available at the following URL:
I passed my OCM 11g exam a year ago now and all requirements are listed here on Oracle Education India website. Please make sure you are serious about passing the exam, its important because it takes lot of efforts and resources (time, money etc) for this exam and I guess you don't want to be disappointed. So study hard and follow Oracle Course guidelines.