Database Crashed. Server manager doesn't come up

This happened to me one fine morning. For one of my databases, DBWR crashed and then all other processes died. After that neither svrmgrl not sqlplus were even starting. These just returned back to unix prompt. The errors in alert log were 600 and 7445 errors. I was running on 7.3.4 on digital unix 4.0D. Shared memory was still allocated for this instance and i was getting 6 trace files in udump directory every 5 minutes.

I Worked with oracle suppport on this. It seemed I had hit a bug resolved in 7.3.4.1 . Solution was to find shared memory segment for victim database by process of elimination using "oradebug ipc" on all other databases and "ipcs -b" on unix prompt and then removing the shared memory segments using ipcsrm (-s or -m for shared memory or semaphores)