Application Continuity on Single instance
Application Continuity is not limited to RAC. It works with Data Guard as well. For example an in-flight transaction can be replayed after a switchover on the new primary (former standby). With a single instance primary and standby, this requires the Active Data Guard option to be licensed.

Application Continuity


  Application Continuity is supported for Oracle Data Guard switchovers
  to physical standby databases. It is also supported for fast-start
  failover to physical standbys in maximum availability data protection
  mode. Note that primary and standby databases must be licensed for
  Oracle RAC or Oracle Active Data Guard in order to use Application
  Continuity.