The system switchover facility provides the following three switchover modes:

• Automatic system switchover
  The running system is switched over automatically when a failure occurs on it.
  
• Planned system switchover
  UNIX edition:
  A cluster software command is executed on the running system to switch over the system intentionally.
  Windows edition:
  The cluster administrator moves a HiRDB group to switch over the system intentionally.
  
• Grouped system switchover
  This is the system switchover mode used when HiRDB is linked to another product, such as an OLTP product. When a failure occurs on the running system, the OLTP product and HiRDB (unit) are grouped, and the grouped system is switched over. With grouped system switchover, you can use either automatic system switchover or planned system switchover. To determine whether you can use grouped system switchover, check your cluster software documentation.