"Translated from MoS article"/DEV/SHM should be set when the Oracle instance starts to not be reported ORA-00845

/DEV/SHM The Oracle instance should be set to start without reporting ORA-00845
From: Ora-00845-which value FOR/DEV/SHM is needed to startup database without ORA-00845 (document ID 1399209.1)

Suitable for:
Oracle Database-standard edition-version 11.1.0.6 and later
Information in this document applies to any platform.
Checked for relevance on 17-jul-2015***

Goal:
Starting with Oracle Database 11g, the Automatic memory Management (AMM) feature requires more shared Memory (/DEV/SHM) and file descriptors
The size of the Shared memory must be at least greater than the Memory_max_target parameter value and memory_target parameter value for each Oracle instance on the host computer.
If the Memory_max_target parameter or the Memory_target parameter is set to a value other than 0, and an incorrect value is assigned to the shared memory, this causes the Oracle instance to fail to start: It will be reported ORA-00845 Error

In a Linux system, if the/DEV/SHM mount size of the operating system system is too small relative to the Oracle SGA and PGA, you will encounter the following error:

Ora-00845:memory_target not supported on the this system.

The cause of this error is insufficient/DEV/SHM allocation. The total memory size of the SGA and PGA, i.e., the Memory_target or memory_max_target set in the initialization parameters, cannot be greater than the shared memory file system (/DEV/SHM) size on your operating system.

Details

The alert log would provide the expected value FOR/DEV/SHM.

Warning:you is trying to use the Memory_target feature. This feature requires THE/DEV/SHM file system to is mounted for at least 1073741824 bytes. /DEV/SHM is either isn't mounted or is mounted with available space less than this size. Please fix the memory_target can work as expected. Current available are 1049145344 and used is 430080 bytes. Ensure the mount point is/dev/shm for this directory. Memory_target needs LARGER/DEV/SHM

Here the alert log confirms:

Current size:1049145344 bytesexpected size:1073741824 bytes (at least)

The current size Of/dev/shm are also confirmed by the ' DF ' command – Current value

# df-k/dev/shmfilesystem 1k-blocks used Available use% mounted ONTMPFS 1024976 420 1024556 1%/DEV/SHM

To fix the current issue the solution would is to allocate at least 1073741824 bytes For/dev/shm.

# mount-t Tmpfs shmfs-o size=1073741824/dev/shm # df-k/dev/shmfilesystem 1k-blocks used Available use% Mounted ONSHMF S 1048576 0 1048576 0%/dev/shm

To retain the value across machine startups, make sure that The/etc/fstab Mount database contains a reference to this new Value, like in:

Shmfs/dev/shm TMPFS size=1073741824 0

"Translated from MoS article"/DEV/SHM should be set when the Oracle instance starts to not be reported ORA-00845