Hi,
I did it; cache problem will be solved later ;-)
However, due to some webhoster limitation, I did it (as always before) using the web-based method (re-run installer). Up to now, the installation end was announced with the page mentioning to rename localsettigs.php etc. But not this time. The installation process ended in that grey box with all the messages after "There are already MediaWiki tables in this database. Checking if updates are needed...". Last message displayed: "Deleting old default messages..."
Running the wiki, all seems to be fine. Special:Version confirms 1.9.2.
But, is the upgrade completed and was it really successful?
And, BTW, I still can't get rid of the old revisions using deleteOldRevisions :-(
Thanks, zaydo