howto prevent automatic close of the Safari browser on iPad / iOS ?

On iPad air (ios 10.3) running Safari 10 the safari browser closes itself after some time of user inactivity and therefore the unsaved Vaadin Flow application form input values are lost.
Does anybody know the exact cause of this (“too” much javascript used and low memory available?) and how to workaround this?

I found these infos related:

[Is Safari closing by itself for anyone else?]
(https://forums.macrumors.com/threads/is-safari-closing-by-itself-for-anyone-else.1816360/)

[Disable automatic application termination in OS X]
(http://hints.macworld.com/article.php?story=20120726192014497)

[iPad Safari crashing regularly, how to fix]
(https://appletoolbox.com/2013/08/ipad-safari-crashing-regularly-fix/)

[Safari quits by itself, no crash reports show up. How do I make it STOP closing/quitting itself?]
(https://discussions.apple.com/thread/5219889)

[Mac 911: Safari consistently quits in Yosemite]
(https://www.macworld.com/article/2955483/software-web/mac-911-safari-consistently-quits-in-yosemite.html)