How IOSCDR retrieves the CDR

There are three ways that IOSCDR can retrieve a CDR:

Directly from the specified device. Specified as READ=IO, this option is slower because it requires I/O, but it provides more current information than READ=NOIO. This option will always give you the CDR that the control unit is currently providing when you issue IOSCDR.
From the system. IOSCDR retrieves the last CDR known to MVS™ for the specified device and path. Specified as READ=NOIO, this option is quicker than READ=I/O, but it is not as current.
Either from the system or directly from the device, depending upon whether the device and path are online. Specified as READ=COND, this option allows the system to decide how to retrieve the CDR. READ=COND returns the most accurate CDR in the shortest time possible, because it performs no I/O if the device and path are online.