In reply to ABD_91:
That answer is not correct.
First of all, randc only works multiple calls to randomize() on the same object; It does not have any effect on the first or only call to randomize().
And second. randc looks at the total solution space for that variable. It just needs to produce a different solution for call to randomize(). So the following solutions meet that criteria
array1 = '{'h0, 'h0, 'h0, 'h0, 'h0, 'h0}
array1 = '{'h0, 'h0, 'h0, 'h0, 'h0, 'h1}
array1 = '{'h0, 'h0, 'h0, 'h0, 'h1, 'h0}
array1 = '{'h0, 'h0, 'h0, 'h0, 'h0, 'h2}
... ~50,000 more possible solutions
If you are just looking for each array element to be unique, use the unique constraint and not randc.
constraint c { unique {array1}; }