Don't understand SORT error message

In a program that does a sort with input- and output-procedures, I get this error message:

I/O error: file 'SORTFILE'

error code: 9/220 (ANS74), pc=0, call=1, seg=0

220   Attempt to execute more than one SORT or MERGE simultaneously

Attached GDC02.txt is the COBOL source code.  What am I doing wrong?