SOLVED: this issue is solved in Linux 6.4 (kernel: 2.6.39-400.17.1.el6uek and 2.6.32-358.el6).
A single entry in /etc/fstab like [tmpfs /dev/shm tmpfs size=3g 0 0] now works as it should!
There is a bug in Red Hat Linux 6 and Oracle Enterprise Linux 6 (UEK and RHEL-kernel) and probably all other Red Hat 6 related Linux Distro’s.
When you need more memory for SGA/PGA when using MEMORY_MAX_TARGET, you need to resize /dev/shm. By default this is 50% of total memory and Oracle tells you to add the following to /etc/fstab, ‘mounting’ the /dev/shm twice (?):
shmfs /dev/shm tmpfs size=3g 0 0
Which works…But, there is another line in /etc/fstab which in my opinion should be used and should work:
#tmpfs /dev/shm tmpfs defaults 0 0 tmpfs /dev/shm tmpfs size=3g 0 0
This works after a remount: ‘mount -o remount /dev/shm’, but it doesn’t work after a reboot…
It seems to be a bug in a module called ‘dracut’. Setting attributes for /dev/shm should work at tmpfs entry, but the attributes are not taken from /etc/fstab :
“Cause: /dev/shm is mounted in dracut without attributes from fstab. Consequence: /dev/shm does not have attributes from fstab. Fix: Remount /dev/shm in rc.sysinit. Result: /dev/shm has attributes from fstab.”
But, adding it again (shmfs see above) to /etc/fstab also works…
This is the case when using the Oracle Enterprise Linux 6 (UEK and RHEL) and Red Hat Linux 6, so I think also Red Hat 6 related distributions like CentOS will suffer from this bug.