Some of IBM’s error messages are more cryptic than others. Copying files from the IFS using CPYFRMIMPF sometimes spits out error messages which are less than clear:
CPYFRMIMPF FRMSTMF('/FOLDER/FOLDER/FILE') TOFILE(*LIBL/FILENAME) MBROPT(REPLACE) RCDDLM(LF) STRDLM(NONE) RMVBLANK(NONE)FLDDLM(TAB) ERRRCDOPT(REPLACE) RPLNULLVAL(FLDDFT)
File system error occurred. Error number 3021
Copy command ended because of error.
Internet Search for CPYFRMIMPF 3021 shows nothing!
How to find CPYFRMIMPF error codes?
Lookup the related CPE error message: DSPMSGD CPExxxx
so, in this case, 3021 means
DSPMSGD CPE3021

In this case the ‘value specified for the argument is not correct‘ is telling us that the FRMSTMF value is incorrect, or file is not found.
Fix the FRMSTMF file name or add some error checking to your program code.