Upgrade from to 9.1 stuck

I'm upgrading my owncloud to 9.1 with occ. the upgrade get stuck on step 5/24 since yesterday morning.

Set log level to debug
Checking whether the database schema can be updated (this can take a long time depending on the database size)
5/24 [=====>----------------------] 20%

There is no errors on log files.

Server configuration
Operating system: Raspbian 8.0
Web server: apache 2.4.10
Database: Mysql 5.5.52
PHP version: 5.6.27
ownCloud version (see ownCloud admin page): upgrade from to 9.1
Special configuration : run on raspberry pi 2

Is it normal?? can I stop and restart upgrade?