That was more than one question… 
So yes the package was installed. I uninstalled it. I’ve tried to reinstall it - but it fails.
As far as I can see 9.6 is installed.
root@ucs-master:/etc# ps aux | grep postgres
postgres 2726 0.0 0.5 267944 24052 ? S 10:12 0:00 /usr/lib/postgresql/9.6/bin/postgres -D /var/lib/postgresql/9.6/main -c config_file=/etc/postgresql/9.6/main/postgresql.conf
postgres 2747 0.0 0.0 267944 3544 ? Ss 10:12 0:00 postgres: checkpointer process
postgres 2748 0.0 0.0 267944 3544 ? Ss 10:12 0:00 postgres: writer process
postgres 2749 0.0 0.0 267944 3544 ? Ss 10:12 0:00 postgres: wal writer process
postgres 2750 0.0 0.1 268360 6456 ? Ss 10:12 0:00 postgres: autovacuum launcher process
postgres 2751 0.0 0.0 123080 2788 ? Ss 10:12 0:00 postgres: stats collector process
root 26441 0.0 0.0 14316 972 pts/1 R+ 10:25 0:00 grep postgres
I followed this.
Is the database »pkgdb« needed for anything else? If not - I will just leave it as it is. I’m not working much with the app.
Thanks for helping out
Bernd