The takeover procedure involves transferring the Primary role from an original Primary to a Secondary. When the original Primary fails or is destroyed because of a disaster, the takeover procedure enables you to convert a consistent Secondary to a Primary. The takeover of a Primary role by a Secondary is useful when the Primary experiences unscheduled downtimes or is destroyed because of a disaster.
In the following illustration, the Primary seattle is replicating to the Secondary hosts london and tokyo when disaster strikes the Primary seattle. The Secondary london has been identified as the Secondary for takeover and will become the new Primary after the takeover is complete.
After the takeover is complete, the Secondary london becomes the new Primary. If you had already created RLINKs between london and tokyo when setting up replication, you do not need to manually reconfigure the additional Secondary tokyo as a part of the RDS. It will automatically be added as a Secondary of the new Primary london.
VVR provides the vradmin takeover command to transfer the Primary role from an original Primary to a Secondary. This command can be run from the Secondary host only when the Primary is not reachable from the Secondary on which the takeover command is to be run. Upon successful completion of the takeover, the Secondary becomes the Primary. VVR displays an error message if you enter the vradmin takeover command on the Primary.