I have run the following code using two different datasets called "masterfile1" and "masterfile2". Masterfil1 is a small test dataset with only a 3x3 covar matrix. Masterfile2 is about 4500x4500.
Masterfile 1 works fine. Masterfile2 gets an "invalid subscript or subscript out of range error".
Thoughts?

proc iml ;
use modiml.masterfile1;
read all var _num_ where (_TYPE_="COV") into x;
call streaminit(0);
N= 5000;
Mean = j(1,&maxcount,0);
COV = x;

x = RANDNORMAL( N, Mean, Cov );

x = (x[1:N,]);
create modimout.singlesim from x;
append from x;
close modimout.singlesim;
quit;
run;