The LOXXX file must be named prefix.BKUP.* or prefix.ARCH.*.
The prefix for the LOXXX file is specified in the $OPTIONS file with the $PREFIX parm. When looking for the LOXXX file, ASM2 looks for the next token after the prefix to be either ARCH or BKUP. Anything else in that position will cause an invalid prefix error. Additional tokens may be added after ARCH or BKUP.
Valid names would include: