You can copy files that contain null-capable fields by using the CPYF and CPYFRMQRYF commands. The FMTOPT parameter allows mapping of null-capable fields.
The INCREL parameter allows the selection of records that are based on whether a field is or is not null.
Record selection involving null values can still be done, but only the user-specified or default value in the buffer (rather than a null value) is copied to the to-file. Null values cannot be preserved in these instances. Any print listings produced when a copy command is run (including TOFILE(*PRINT), PRINT(*COPIED), PRINT(*EXCLUDE), and PRINT(*ERROR)) also ignore null values.