p1,m1,f1

These variables specify a field in the input record to be compared either to another field in the input record or to a constant.

p1 specifies the first byte of the compare field relative to the beginning of the input record.¹ The first data byte of a fixed-length record (FLR) has relative position 1. The first data byte of a variable-length (VLR) record has relative position 5 (because the first 4 bytes contain the record descriptor word). All compare fields must start on a byte boundary, and no compare field can extend beyond byte 32752.
m1 specifies the length of the compare field. Acceptable lengths for different formats are in Table 1.
f1 specifies the format of the data in the compare field. Permissible formats are given in Table 1.
You can use p1,m1 rather than p1,m1,f1 if you use FORMAT=f to supply the format for the field.

Table 1. Compare Field Formats and Lengths
Compare Field Formats and Lengths Format Code	Length	Description
CH	1 to 256 bytes	Character ²
AQ	1 to 256 bytes	Character with alternate collating sequence
ZD	1 to 256 bytes	Signed zoned decimal
PD	1 to 255 bytes	Signed packed decimal
PD0	2 to 8 bytes	Packed decimal with sign and first digit ignored
FI	1 to 256 bytes	Signed fixed-point
BI	1 to 256 bytes	Unsigned binary
AC	1 to 256 bytes	ASCII character
CSF or FS	1 to 32 bytes	Signed numeric with optional leading floating sign
UFF	1 to 44 bytes	Unsigned free form numeric
SFF	1 to 44 bytes	Signed free form numeric
CSL or LS	2 to 256 bytes	Signed numeric with leading separate sign
CST or TS	2 to 256 bytes	Signed numeric with trailing separate sign
CLO or OL	1 to 256 bytes	Signed numeric with leading overpunch sign
CTO or OT	1 to 256 bytes	Signed numeric with trailing overpunch sign
ASL	2 to 256 bytes	Signed ASCII numeric with leading separate sign
AST	2 to 256 bytes	Signed ASCII numeric with trailing separate sign
D2	1 to 256 bytes	User-defined data type (requires an EFS program)
Note: See Data format descriptions for detailed format descriptions.