Hi,
In Screen components, active component influence other components like input, output and invisible.
From F1 Help,
The active component does not have a corresponding
attribute. A change to its content using MODIFY SCREEN
influences the input, output
and invisible attributes, and correspondingly the
input, output and invisible components of the structure SCREEN.
If you put the break-point in your code before and after Modify screen below, you can easily find out all other components like input , output and invisible attributes are getting changed after MODIFY screen.
IF screen-name = 'P_PERNR1'.
screen-active = '0'.
MODIFY SCREEN.