Problem:

using the following mfsort instructions gave the error SORT(EXTSM) failed - sort engine status = 39:

INREC FIELDS=(0001:0021,0020,      

                   0021:1970,0008)     

* SORT FIELDS=(0001,0020,CH,A)

  SUM FIELDS=(0021,0008,PD)  

use d:\\input.dat

   org SQ

   record (f 5940)

give d:\\output.dat

  org SQ

  record (f 28)

Resolution:

Problem was due to the SORT statement being commented out.  Since no SORT key is specified it assumes that the entire input record will be used as the sort key.

The input record in this case is of size 5940 which is beyond the maximum allowable size for a sort key (4096).  Including a SORT statement that uses a sort key that is less than 4096 in size fixed the problem.