The following describes the PPRC synchronous copy functions:
- A PPRC data copy to the recovery storage subsystem is synchronous
with the primary volume’s I/O operation. This means that the primary
system writes data to a primary volume’s storage subsystem, the
data is transferred to cache and nonvolatile storage (NVS), and the
storage control sends channel end status to the host.
- The primary site storage control then initiates an I/O channel
program to the recovery site storage control to transfer the updated
data.
- The primary site storage control returns device end status to
the primary system when the transfer to the recovery site storage
control cache and NVS is complete.
- The primary system notifies the application program that the operation
is complete.
Note: The PPRC copy function does not consider the primary
system DASD write operation complete until the data that is sent to
the recovery storage subsystem has received channel end and device
end status from the secondary volume storage control. Each primary
system write to the recovery subsystem causes an increase to the primary
system response time.