A synchronization confirmation method required for operation of a database is
provided
to a host device connected to a disk device which provides remote asynchronous
data transfer. Immediately after commit of write data, an application of the host
device issues a sync command which requires synchronization confirmation. A disk
control device notifies the host device of a number concerning latest data received
from the host device of a local side and a number concerning latest data received
by a remote side. When the two numbers have coincided with each other, the host
device judges the commit operation to have been completed.
