Increasing size of tmpfs (/dev/shm)

/dev/shm is nothing but implementation of traditional shared memory concept. It is an efficient means of passing data between programs. One program will create a memory portion, which other processes (if permitted) can access. This will result into speeding up things on Linux.
In oracle 11g if you choose automatic memory management then the size of /dev/shm will definitely to be an optimum value.

how to increase:

To increase or decrease /dev/shm filesystem size

1) Open /etc/fstab with vi or any text editor of your choice,

2) Locate the line of /dev/shm and use the tmpfs size option to specify your
expected size, e.g. 512MB:
tmpfs /dev/shm tmpfs defaults,size=512m 0 0

e.g. 2GB:
tmpfs /dev/shm tmpfs defaults,size=2g 0 0


The /etc/fstab content format is documented in man fstab and the tmpfs filesystem options can be found in man mount

3) To make change effective immediately, run this mount command to remount the /dev/shm filesystem:

mount -o remount /dev/shm


Note: Database services will be aborted immediately while remounting. So better if you shut your database first and then change the size.

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