Query for open replicator - Hot pull or pull

Hello Guys,,

I have a doubt that using Open replicator PULL or HOT PULL mode...

Does the remote device must need be offline to hosts ???

if yes,, please suggest ,, as I have to migrate data from VNX ( having production luns )  to VMAX 3 .

Which method I can use for SAN based migration where VNX production luns can be available online to production servers during the migration time..