field katr1

hi abappers,

I need know raally the mean of the next code:

IF KNA1-KATR1 EQ SPACE."in my case this field is empty, Is it space?
CLEAR TVK1T." clear all text in all languages?
ELSE.
IF TVK1T-SPRAS NE SY-LANGU
OR TVK1T-KATR1 NE KNA1-KATR1,
SELECT SINGLE * FORM TVK1T
WHERE SPRAS = SY-lANGU
AND KATR1 = KNA1-KATR1.

IF SY-SUBRC NE 0.
CLEAR TVK1T.
ENDIF
ENDIF
ENDIF

IF KNA1-KATR2 EQ SPACE.
CLEAR TVK2T.
ELSE."in my case this field is 1A
IF TVK2T-SPRAS NE SY-LANGU "what expect it, all code if?
OR TVK2T-KATR2 NE KNA2-KATR2,
SELECT SINGLE * FORM TVK2T
WHERE SPRAS = SY-LANGU
AND KATR2 = KNA2-KATR2.

IF SY-SUBRC NE 0.
CLEAR TVK2T.
ENDIF
ENDIF
ENDIF

I belive that the code change the fields reserved in the customer master record (KNA1), but when I modify value with a batch input, calling to program include SAPLV02Z in the screen 0100, the batch input return error on mode N; when I pass the batch input on mode A the batch input no return error, but I want know why...

I hope you help me, please.

...
'X' 'SAPLV02Z' '100',
' ' 'KNA1-KATR1' L_MARK,
' ' 'KNA1-KATR2' PE_SITUATION,
...

Can you help me please.?

In the module KNA_ATRIBUTE_TEXT. (include LV02Z0KA) of program SAPLV02Z

Cordial greetings.