what does the msg "unexpected oracle server termination by signal 6" mean?

I had installed an Oracle version 6.0 on a VAX 3300 running Ultrix 4.3. Unfortunately, the maintenance people brought down the system last month without first shutting down the oracle. Now, I could NOT restart the whole thing. The following is a script that shows what happened. I'll appreciate for any pointers. Please e-mail me directly. Thanks in advance. -- Wang

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% sqldba

SQL*DBA: Version 6.0.27.9.1 - Production on Wed Mar 31 10:10:03 1993

Copyright (c) Oracle Corporation 1979, 1989. All rights reserved.

ORACLE RDBMS V6.0.27.9.1, transaction processing option - Production PL/SQL V1.0.28.1.0 - Beta

SQLDBA> startup
ORACLE instance started.
Database mounted.
Unexpected oracle server termination by signal 6 ***** core dumped at this point ....

IPC status from /dev/kmem as of Wed Mar 31 10:10:33 1993 Message Queues:
T ID KEY MODE OWNER GROUP QBYTES *** No message queues are currently defined ***

Shared Memory
T ID KEY MODE OWNER GROUP SEGSZ

m   1300    1444688 --rw-r-----   oracle    users 131072
m    101   18221904 --rw-r-----   oracle    users 131072
m    102   34999120 --rw-r-----   oracle    users 131072
m    103   51776336 --rw-r-----   oracle    users 131072
m    104   68553552 --rw-r-----   oracle    users 131072
m    105   85330768 --rw-r-----   oracle    users 114688

Semaphores
T     ID     KEY        MODE       OWNER    GROUP NSEMS
s     10          0 --ra-r-----   oracle    users    20

%
script done on Wed Mar 31 10:10:42 1993 Received on Mon Apr 19 1993 - 09:25:13 CEST