SORT Manual says:
The REFORMAT statement indicates the fields from the F1 file and/or the F2 file you want to include in the joined records, and the order in which you want the fields to appear. You can also include an indicator of where the key was found in the joined records ('B' for key found in F1 and F2, '1' for key found in F1 only, or '2' for key found in F2 only).
Joined: 09 Mar 2011 Posts: 7309 Location: Inside the Matrix
The Fn:1,1 and then test for space is a SyncSort technique because SyncSort does not have the ? marker. You need to choose a location which cannot possibly have that value, so doesn't need to be 1,1, you can change the fill character (used to create "no data" for a mismatch) to another value as well.
Yes, your REFORMAT can contain data from both files. Most often it will. Where there is a mismatch, the data from the file which did not match gets set to a "pad" value.
Yes, the ? indicator will still tell you the "condition" of the JOIN. B, 1 or 2, and this is 100% reliable without expending effort choosing a location/different pad value.