if you terminate your clone session ..DMX stops tracking changes between source and target device (SDDF session), but the data on the target device is still valid.

so the process is to create device group, assign source devices to it, assign target devices to it using -tgt option at the end of your symld command, create the group (using -copy or -precopy in addition to -differential if you need to do incremental synchs later on) and last step is to activate. As soon as you activate you take a point in time copy of the source luns ..even though in the background data is still being copied to the target devices (-copy option).

At what point are the LUNs mountable to the "target" system in a R/W mode, after the "activate" or the "terminate"?

Hopefully I will get some advance notice when this process needs to be done so that I can insure that the copy is complete, but if not, how can I tell when the copy is 100% complete. Or is that a moot point due to the PIT functionality?