REXX variables, when first used, have their name in upper case assigned as a value. This is of little use if the array is to be used for numeric purposes when an initial value of zero is usually required. The conventional method is to loop over each array element setting it to zero. This is wasteful and always assumes that the number of array elements to be used is known before the program runs.
Conventional method
do I=1 to 30 ARRAY.I=0 end
Suggested method
ARRAY.=0
or
parse value 0 with ARRAY.