Return codes

Here is a list of return codes that explains the results of the conversion invocation.
 0
No warnings, errors, or severe errors
 1
All messages were suppressed.
 4
CANCEL command ended ISPDTLC
 8
Only warnings were found
16
At least one DTL conversion had at least one error
20
At least one DTL conversion ended with a severe error.

For multiple conversions, the highest return code is used.