Records may be covered by "access controls" to regulate who can access them and under what circumstances. Physical controls may be used to keep confidential records secure – personnel files, for instance, which hold sensitive personal data, may be held in a locked cabinet with a control log to track access. Digital records systems may include role-based access controls, allowing permissions (to view, change and/or delete) to be allocated to staff depending on their role in the organisation. An "audit trail" showing all access and changes can be maintained to ensure the integrity of the records.