AFAIK "precopy" simply doesn't make sense in hot pull rcopy operations.  When you copy data between storages with Open Replicator you need to set the "point in time" of the copy. Either with a push or a pull session you set the PIT when you activate the session. When you push from the controlling device to the target, the controlling device is aware of the writes it receives. Thus when you run a push session you can pre-copy data on the target and eventually copy it again in case the host changes data on the source. On the other side, when you pull data from another storage to the target (which is at the same time the controlling device) you can't copy any data BEFORE activating the session. Simply becouse you can't know when the data changes on the source side. Thus precopy simply doesn't makes sense with pull sessions.
why can not we use -precopy option in hot pull option? 
SYMRCOPY