Update 9.12 Error "oc_filecache"

Dear all,
I have 3 OC Instances running for 3 Domains, at least one of them only as test environment.
I upgraded successfully 2 instances from 9.1.0.15 to 9.1.2.5. Now, on my biggest cloud I ran into the following error
[5/ 24] Überprüfe Tabelle oc_filecache
Ein Fehler ist aufgetreten
(translation: 5/24 checking table oc_filecache : An error occured)
The Cloud there has a total size of 180 GB,the whole sql database has a size of 150 MB.
The table oc_filecache has 503397 rows. Deleting these rows is harmful as it kills the access to encrypted data. I guess that the filecache is too big for the migration process. Is there a workaround to handle the upgrade or a solution to shrink the database?
Thank you in advance an best regards
Michael

You should run the occ upgrade command from command line; this way you don't risk to run into timeouts. The size of the table is not very large, this should be a problem. It seems that there is an issue with the table itself, so put your owncloud into maintenance mode, then use mysql-command to check (and repair) the tables. Finally, run the upgrade command from terminal.

Is this in a hosted environment or a vserver/arm-board with very limited resources?