What does a * mean for checktable in dd03l?

I am looking at dd03l, there is a column checktable which tells the check table

For the filedname in a given table tabname.

I have seen following values in checkable:

1. Blank u2013 no check table

2. A table name such T005, it is the check table name

3. * - a star

I do not know what is the meaning of a *.

Appreciate your answer?