How to delete all Un-Excluded Lines in ISPF
Generally you would have used :
x all; find all <criteria>; del x all
It deletes all lines you have excluded (and don’t need any more) in your dataset.
Here we have different scenario:
We want to exclude all lines that meets a <criteria> and then delete all lines that don’t meet the <criteria> …
 x all <criteria>
It will exclude all lines having the <criteria>
Now read carefully
Now you want to delete all visible lines and keep all excluded lines (which meets your <criteria>)…………..
and unwanted lines are now visible to you.
you want to delete these all visible (unwanted) lines.
the command you have to issue is :
 del all nx
it will keep all excluded lines and delete all visible lines.
You will see all the lines are excluded in your dataset,
Just issue reset command and view the result..
Got it ??? !!!!