That’s strange. I can’t see why removing a non-used shared memory segment would
crash any database.
Meanwhile, Stefan has already suggested a better way for identifying shared
memory segments belonging to a particular database.
sysresv
Shared Memory:
ID KEY
905970099 0x00000000
905970100 0x00000000
905970101 0x00000000
905970098 0x00000000
905970102 0x6073fcb8
The dead segments can be removed by ipcrm –m shmid
Expectedly, the segments listed by sysresv match the ipcs –am output, which
also shows some additional information, such as the number of attached
processes, last access time etc.:
ipcs -am | grep 905970
m 905970102 0x6073fcb8 --rw------- oracle dba oracle dba
64 20480 23319 28463 19:23:10 19:23:10 10:04:51
m 905970101 0x0 --rw------- oracle dba oracle dba
64 92274688 23319 28463 19:23:10 19:22:56 10:04:51
m 905970100 0x0 --rw------- oracle dba oracle dba
64 973078528 23319 28463 19:23:10 19:22:56 10:04:51
m 905970099 0x0 --rw------- oracle dba oracle dba
64 3221225472 23319 28463 19:23:10 19:22:56 10:04:51
m 905970098 0x0 --rw------- oracle dba oracle dba
64 10485760 23319 28463 19:23:10 19:22:56 10:04:51
So for safety reasons, both outputs can be compared before removing any
segments.
Nenad
https://nenadnoveljic.com/blog/
From: Jeff Chirco <backseatdba@xxxxxxxxx>
Sent: Donnerstag, 7. Februar 2019 18:21
To: Noveljic Nenad <nenad.noveljic@xxxxxxxxxxxx>
Cc: Mark W. Farnham <mwf@xxxxxxxx>; oracle-l-freelist <oracle-l@xxxxxxxxxxxxx>
Subject: Re: clone creations fails with shared memory realm already exists
Ok that apparently crashed a few of my dev databases that were running when I
did that. I got reports of errors and when I tried to log in to database it
said shared memory realm already exists. I ran a ps -ef | grep for the
database name and found a bunch of processes still running. Killed the pmon
and they all dropped and I was able to restart the database. No harm done as
it is just Dev but I don't think anyone will want to do this on a Production
system with other running databases, maybe if they are all down.
Jeff
On Thu, Feb 7, 2019 at 8:56 AM Jeff Chirco
<backseatdba@xxxxxxxxx<mailto:backseatdba@xxxxxxxxx>> wrote:
Thanks Mark and Nenad, removing the dead segments worked. Learned something
today!
Jeff
On Thu, Feb 7, 2019 at 7:38 AM Noveljic Nenad
<nenad.noveljic@xxxxxxxxxxxx<mailto:nenad.noveljic@xxxxxxxxxxxx>> wrote:
You’d need to look for a segment with no attached processes (NATTACH=0). It’s a
dead segment that can be removed with ipcrm.
IPC status from <running system> as of Thu Feb 7 16:34:40 MET 2019
T ID KEY MODE OWNER GROUP CREATOR CGROUP
NATTCH SEGSZ CPID LPID ATIME DTIME CTIME
Shared Memory:
m 1560281188 0x2a54d290 --rw------- oracle dba oracle dba
453 28672 8707 24484 16:34:33 16:34:33 8:47:09
m 905969763 0x0 --rw------- oracle dba oracle dba
453 329252864 8707 24484 16:34:33 16:34:33 8:47:09
…
Best regards,
Nenad
https://nenadnoveljic.com/blog/
From: oracle-l-bounce@xxxxxxxxxxxxx<mailto:oracle-l-bounce@xxxxxxxxxxxxx>
<oracle-l-bounce@xxxxxxxxxxxxx<mailto:oracle-l-bounce@xxxxxxxxxxxxx>> On Behalf
Of Jeff Chirco
Sent: Donnerstag, 7. Februar 2019 16:33
To: Mark W. Farnham <mwf@xxxxxxxx<mailto:mwf@xxxxxxxx>>
Cc: oracle-l-freelist <oracle-l@xxxxxxxxxxxxx<mailto:oracle-l@xxxxxxxxxxxxx>>
Subject: Re: clone creations fails with shared memory realm already exists
Hi Mark not sure what to look for with that. There is 22 other databases
running on this server. Its a dev server with a bunch of clones and little use.
On Wed, Feb 6, 2019 at 7:41 PM Mark W. Farnham
<mwf@xxxxxxxx<mailto:mwf@xxxxxxxx>> wrote:
see what ipcs –m says is allocated.
From: oracle-l-bounce@xxxxxxxxxxxxx<mailto:oracle-l-bounce@xxxxxxxxxxxxx>
[mailto:oracle-l-bounce@xxxxxxxxxxxxx<mailto:oracle-l-bounce@xxxxxxxxxxxxx>] On
Behalf Of Jeff Chirco
Sent: Wednesday, February 06, 2019 10:05 PM
To: oracle-l-freelist
Subject: clone creations fails with shared memory realm already exists
Ok I am confused. I am trying to make a thin clone of our database from one
server to another. Something I have done many times. I use NetApp Snap Manager
for Oracle. Oracle EE 12.2.0.1 running on Oracle Linux 7. The clone process is
failing with ORA-27100: shared memory realm already exists.
This database does not currently exist. I ran a ps -ef | grep for my database
name and no process are found. There is nothing in /etc/oratab. I've tried
adding an entry to make sure a database with that name is not running. There
is no pfile, spfile, password file. I've checked /dev/shm for any files
related to my database name and there is nothing. I don't understand by it
thinks shared memory realm already exists.
Any suggestions?
Thanks,
Jeff
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