# Overview of freezing and locking

Freezing and locking data allows you to prevent changes in forms, either temporarily during a study or permanently at the end of a study.

You can freeze and lock:

- Forms
- Visits
- Case report books

Note: You can only freeze or lock a form in which a user has entered at least one data item or comment. If you freeze or lock a case report book, freeze or lock icons appear only on started forms; however, all forms in the case report book are frozen or locked. The activities that are allowed, or not allowed, pertain to all forms. For more information, see Rules for freezing and locking.

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