I have registered Salesforce DEV 401 certification. how many times are possible to reschedule registered exam online protocard.
If you log in to webassessor (the third party for Salesforce's exams), and then click on the help click, you will find information on exam registration. Salesforce's suggestion is to open a case with them to reschedule your exam. Note, they'll be best suited to answer the how many times can I re-register question.
This is what my exam registration confirmation email says -
Cancellation and Reschedule policy:
If you wish to cancel or reschedule without any additional fees you can do so as long as a minimum of 72 hour advance notice is given prior to the scheduled start time. You can make the change on your own by logging into your Webassessor account, clicking on the details of your scheduled exam and then clicking on the "Reschedule" or "Cancel" button. If the 72 hour window has passed, you will have to pay $75 to reschedule or cancel. To do so, please open a case with the Salesforce.com Certification team at http://certification.salesforce.com/open-a-case. Cancellations or Reschedules are not accepted by phone. If you do not take the exam at the scheduled time and do not cancel before the scheduled time, you will be charged the full exam fee.