If we face ORA-00845
during database startup, it would mean that /dev/shm file system is not
configured with appropriate value required to start the database instance. We
need to mount /dev/shm with a value that should be equal or more than the value
of memory we want to allocate to all instances/SGAs (ASM as well as database
instances) that would run on this host.
WARNING: You are trying to use the MEMORY_TARGET
feature. This feature requires the /dev/shm file system to be mounted for at
least 914358272 bytes. /dev/shm is either not mounted or is mounted with
available space less than this size. Please fix this so that MEMORY_TARGET
can work as expected. Current available is 911679488 and used is 667967488
bytes. Ensure that the mount point is /dev/shm for this directory.
Thu Mar 17 11:05:27 2016
memory_target needs larger /dev/shm
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Above warning is
because of low allocation to /dev/shm, as can be seen bellow.
[root@salman1 ~]# df -kh
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 116G 24G
86G 22% /
/dev/sda1 1008M 78M
880M 9% /boot
tmpfs 1.5G 0
1.0G 66.6% /dev/shm
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To fix this problem, we
should add an entry similar to the following /etc/fstab file so that /dev/shm
is set automatically after every server startup. I am setting /dev/shm to 8G
for this example.
tmpfs /dev/shm tmpfs defaults,size=8G 0 0
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Now shutdown all
instances (ASM and/or database) currently running (if any), and unmounts
/dev/shm.
[root@salman1 ~]# umount -l /dev/shm
[root@salman1 ~]# df -kh
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 116G 24G
86G 22% /
/dev/sda1 1008M 78M
880M 9% /boot
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Issue following command
to mount /dev/shm again based on the value set in /etc/fstab file, and check if
this file system has been set to 8G.
[root@salman1 ~]# mount -a
[root@salman1 ~]# df -kh
Filesystem Size Used Avail Use% Mounted on
/dev/sda3 116G 24G
86G 22% /
/dev/sda1 1008M 78M
880M 9% /boot
tmpfs 8.0G 0
8.0G 0% /dev/shm
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