Hi Volker,
does a db_state really show the state online?
As I could see, you get an error
| 2013-03-26 10:30:14 | 30400 ERR | -24574 DBMSrv ERR_EVENTING: Error in eventing occurred. |
| 30400 ERR | -24994 DBMSrv ERR_RTE: Runtime environment error |
in dbm.prt.
So you could try to disable the event dispatcher as mentioned in
Note 895992 - Database does not start: ERR_NODISPATCHERSTART and try if the database comes up.
Maybe the DB has problems sending the mail or creating the bad indexes via event.
If this does not work I would suggest to open a message at SAP.
Best regards
Christian