Designates a table function as the controlling copy of all other copies of the table function running on other AMP vprocs.
Setting up a controlling copy of a table function is useful when there is a need to distribute certain external control data among various copies of the table function that run on different AMP vprocs, but the external control data is on a particular node that only one copy of the table function can access.
Only one copy of the table function can successfully call Tbl.control().
After calling Tbl.control(), the controlling copy of a table function can distribute control data to other table function copies by calling Tbl.setCtrlCtx().
This method returns true if the call is successful and the copy of table function can take the control role of the table function. If the method returns false, the copy of the table function should not assume the role of the control copy.