The references to the data tables are "dt" and "dtLimits".
close( dt, nosave );
will close the data table called Big Class
Or if you need to add a new column to that data table it would be
dt << new column("my column", formula(:height*:weight);;
and if you want to reference the limits table, such as to get the _std Dev value for the :height column, you can get it with
height_Std_Dev = dtLimits;height[4];
where the _Std Dev value in in the 4th row of the height column in the dtLimits data table.
or getting fancier
height_Std_dev = :height[(dtLimits << get rows where(:_LimitsKey == "_Std Dev"))[1]];
Scoping and data table referencing are documented in the Scripting Guide. For JMP 10 it is found under
Help=>Books=>Scripting Guide
Jim