How can I determine the Message Data Start Position on the ADDRPYLE Command?

This information is in the message description. For example, to add message CPA4002 to your System Reply List and to have the message be responded to automatically for one particular printer only, use the name of the printer for the Comparison Data field in the Add Reply List Entry (ADDRPYLE) command. The printer name must be in capital letters.

To find the Message Data Start Position or Compare Start, do a DSPMSGD on the CPA4002 message. You can see from the message text that the printer name is at variable &3. Take Option 2 from the menu to display the field data. On this screen you can see that the variable at &1 is a character field with a length of 10. Variable &2 is also a character field with a length of 10. The compare start for variable &1 would be 1. Add the 10 character field of variable &1 to this compare start and you see that the compare start for variable &2 would be 11. Then you would add the 10 character field of variable &2 to the 11 and find that the compare start for variable &3, the printer name, would be 21. The Message Data Start Position on the ADDRPYLE command would be 21.