I happened to have a FINDREP with a big number of hex values (256, or all of them). Slight variation on Kolusu's method, the intention being to strain the CPU less...

Firstly, remove the X'nn' for all the values which are valid for you (paying attention to whether space is OK, for instance).

The FINDREP will operate zero (all characters in every position valid) or once (one character, somewhere, not valid). If one invalid character is found, the data on the record will be from that point on will be shifted one character to the left. So, due to the padding character which will be inserted in the last position of the record being space, the record will not be OMITted. If no invalid character is found, the C'1' will still be where it was placed in the OVERLAY, and the record will be OMITted on OUTFIL.

INREC INREC=(WHEN=INIT,OVERLAY=(1592:1,1591,C'1')),

IFTHEN=(WHEN=INIT,FINDREP=(IN=(X'00',

X'01',X'02',X'03',X'04',X'05',X'06',X'07',X'08',X'09',

X'0A',X'0B',X'0C',X'0D',X'0E',X'0F',X'10',X'11',X'12',X'13',

X'14',X'15',X'16',X'17',X'18',X'19',X'1A',X'1B',X'1C',X'1D',

X'1E',X'1F',X'20',X'21',X'22',X'23',X'24',X'25',X'26',X'27',

X'28',X'29',X'2A',X'2B',X'2C',X'2D',X'2E',X'2F',X'30',X'31',

X'32',X'33',X'34',X'35',X'36',X'37',X'38',X'39',X'3A',X'3B',

X'3C',X'3D',X'3E',X'3F',X'40',X'41',X'42',X'43',X'44',X'45',

X'46',X'47',X'48',X'49',X'4A',X'4B',X'4C',X'4D',X'4E',X'4F',

X'50',X'51',X'52',X'53',X'54',X'55',X'56',X'57',X'58',X'59',

X'5A',X'5B',X'5C',X'5D',X'5E',X'5F',X'60',X'61',X'62',X'63',

X'64',X'65',X'66',X'67',X'68',X'69',X'6A',X'6B',X'6C',X'6D',

X'6E',X'6F',X'70',X'71',X'72',X'73',X'74',X'75',X'76',X'77',

X'78',X'79',X'7A',X'7B',X'7C',X'7D',X'7E',X'7F',X'80',X'81',

X'82',X'83',X'84',X'85',X'86',X'87',X'88',X'89',X'8A',X'8B',

X'8C',X'8D',X'8E',X'8F',X'90',X'91',X'92',X'93',X'94',X'95',

X'96',X'97',X'98',X'99',X'9A',X'9B',X'9C',X'9D',X'9E',X'9F',

X'A0',X'A1',X'A2',X'A3',X'A4',X'A5',X'A6',X'A7',X'A8',X'A9',

X'AA',X'AB',X'AC',X'AD',X'AE',X'AF',X'B0',X'B1',X'B2',X'B3',

X'B4',X'B5',X'B6',X'B7',X'B8',X'B9',X'BA',X'BB',X'BC',X'BD',

X'BE',X'BF',X'C0',X'C1',X'C2',X'C3',X'C4',X'C5',X'C6',X'C7',

X'C8',X'C9',X'CA',X'CB',X'CC',X'CD',X'CE',X'CF',X'D0',X'D1',

X'D2',X'D3',X'D4',X'D5',X'D6',X'D7',X'D8',X'D9',X'DA',X'DB',

X'DC',X'DD',X'DE',X'DF',X'E0',X'E1',X'E2',X'E3',X'E4',X'E5',

X'E6',X'E7',X'E8',X'E9',X'EA',X'EB',X'EC',X'ED',X'EE',X'EF',

X'F0',X'F1',X'F2',X'F3',X'F4',X'F5',X'F6',X'F7',X'F8',X'F9',

X'FA',X'FB',X'FC',X'FD',X'FE',

X'FF'),OUT=C'',DO=1,STARTPOS=792,ENDPOS=1584))

OUTFIL OMIT=(1585,1,CH,EQ,C'1'),

BUILD=(1,1591)