Data Comparison. Describe Objects

I have two databases with each schema containing 171,000 tables(Since it is an ERP application). I want to compare a select few tables only, but first I need to load all the objects.

Steps performed:

1. select New data comparison option

2. Select source and target.

3. Select schema.

Problem 1: It starts to first describe and map objects. Roughly takes 3-4 hours to even bring up the tables to compare list.

Problem 2: After the objects are described, I saved it to file as .dcomp. When I open this file the next run, I expect that all objects are available, but it starts to describe objects again and takes 3-4 hours.

What am I missing?

Regards

Shivanand Mali