While not required by the Department of State for consular visa interviews, international students and scholars sometimes wish to provide letters to a family member who is applying for a visitor visa to come to the U.S. for a short time. The U.S. Department of State includes this information on its website, and confirms that letters of invitation or Affidavits of Support are not needed as part of the visa application process.
OVIS does not provide enrollment verification letters. Undergraduates can obtain enrollment verification through DartHub. Graduate students can obtain enrollment verification through their Registrar's office.
If you would like to provide a more detailed letter for your family member, or for a non-relative, you may choose to do so yourself. OVIS provides a sample template letter that you are welcome to use. If you are graduating you can obtain information about the ceremony date and time on your school's website.