IBM 3270 Manual page 23

To make another window active:
1. Press the Jump key.
The double border will move to the next
window in alphabetical order. The windows
are kept in alphabetical order by their
single-letter short names. The short name is
shown first in the upper left corner of the
border.
2. To make the next window in order active,
press the Jump key again.
3. To get back to the first window again, keep
pressing the Jump key.
There is another way to make windows active.
1. Press the WSCtrl key.
2. Type the short name of the window you want.
The window with the name you type will
become the active window.
3. Press the WSCtrl key again to go back to
your work.
If you have windows that overlap on your screen,
you will see some interesting effects when you
choose a new window. The active window will
always be on top. The other windows may be
completely or partly covered.
2-4 Book 3 - Using the Control Program