Question: What causes the ORA-11081 error,  The cause and action in the documentation is nit helpful, and I need to be able to re-start my Oracle database after a system crash even though the ORA-01081 message says that Oracle is already running!  How do I fix the ORA-01081 error?  I have both Windows and Linux/UNIX servers running Oracle.

Answer:  The ORA-01081 error that ocues right after a system issue (where you cannot connect to the database) usually means that you have "held" RAM segments that need to be cleaned up.

 ORA-01081 on Linux/UNIX

When you are forced to terminate a half-running Oracle instance on a UNIX or Linux server, you have to perform the following steps:

1. Kill all Oracle processes associated with the ORACLE_SID
2. Use the ipcs –pmb command to identify all held RAM memory segments, the then use the ipcrm –m command to release the RAM memory from UNIX.
   (non_AIX only) Use the ipcs –sa command to display held semaphores and then use the ipcrm –s command to release the held semaphores for the instance
   

For the Oracle professional, it is easy to create a single command to terminate all Oracle processes associated with your hung database instance.  In the example below, we use the ps command to identify the Oracle processes and then use the awk utility to extract the process ID (PID) for the Oracle processes.  We then pipe the process ID into the UNIX kill command:

root> ps -ef|grep $ORACLE_SID| \
      grep -v grep|awk '{print $2}'|xargs -i kill -9 {}  

Now, after we have killed all Oracle processes, we can then check for held memory using the ipcs –pmb command and remove the memory held by the database.  We start by displaying all held memory segments on the database server.
root> ipcs -pmb


IPC status from /dev/kmem as of Mon Sep 10 16:45:16 2001
T      ID     KEY        MODE     OWNER  GROUP  SEGSZ  CPID  LPID
Shared Memory:
m   24064 0x4cb0be18 --rw-r----- oracle    dba 28975104  1836 23847
m       1 0x4e040002 --rw-rw-rw-   root   root    31008   572   572
m       2 0x411ca945 --rw-rw-rw-   root   root     8192   572   584
m    4611 0x0c6629c9 --rw-r-----   root   root  7216716  1346 23981
m       4 0x06347849 --rw-rw-rw-   root   root    77384  1346  1361

Here we see that the only RAM memory segment owned by Oracle is ID=24064.  The following command will release this memory segment:

root> ipcrm –m 24064

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