A rollback reverts a system, application, or configuration change to its previous state. You perform one when an update or change causes unexpected problems. The prerequisite is a defined restore point created before the change — such as a snapshot, a database backup, or a version tag in configuration management. In an ISMS, a documented rollback procedure is part of change management per ISO 27001 Annex A 8.32. Test rollbacks regularly so they work reliably when needed.