When modeling in Xcalar, there are two techniques to monitor memory utilization by tables. Both can be found in Xcalar Design (the user gui) on the Monitor->System panel.
Method 1) on the left edge of the screen you will see a menu-option which says Release Memory, with a trash can icon next to it.
click on that icon and it will display the Drop Table dialogue which will list all of your existing tables - and show the size of each. By the way there are three categories of tables that it will show
a) Active (this is most recent version of the tables you are working with)
b) Hidden (if there are any, they are versions of tables which you have chosen to keep but hide from display to avoid clutter)
c) Temporary (these are prior versions of tables which have been saved so that you can instantly revert if you wish - you should delete this once you know you have no need to revert back to them)
Displaying these tables does not risk dropping them. If you do wish to drop any, you must click on them and then subsequently click on the Drop Tables button in the lower right).
Method 2) on the main body of the System->Monitor you will see a graphical display of ALL memory on the entire Xcalar cluster, how it is allocated, and how much is consumed vs how much is free. This will report all datasets and tables for all users of the Xcalar cluster.