Atomic checkins Team Foundation Server enforces atomic check-in to help maintain the integrity of files under source control. When a user checks in files to Team Foundation Server, all of the changes are collected into an atomic unit called Change Set. If a check in fails, then none of the changes collected in Change Set are committed. For example, if a check in fails while a user is adding several files to a project, Change Set collects this information but does not commit it—preventing incomplete information from being added to a project. Atomic check-in also ensures that check-in policies are enforced and check-in notes are collected. As part of the check-in process, Change Set is checked against all policies and all mandatory notes are collected before a check in is completed. For example, if one file in Change Set violates a check-in policy, then no files in Change Set will be checked in. A Change Set containing multiple files