Delphix Products

Off a single dSource, I created VDB_X and VDB_Y at the same point in time.

I then run the same large upgrade script against both VDB_X and VDB_Y that updates a majority of the DB blocks. Is Delphix able to recognize that while the VDBs have significantly diverged from the dSource, I have two large VDBs with the same data, so I only keep "one copy?"

Since you have already created a branch with your VDB's then the data is completely different and separate, no matter how identical the composite. . In a tree analogy, you might have identical twigs and leaves, but you are two different branches now.

In that model, and if the amount of data is that significant, I would suggest that you have a Trunk VDB and apply the large update to the trunk VDB and then refresh the branches (VDB_X & VDB_Y).