The size of in-memory file system mounted at /dev/shm is “259072” megabytes which does not match the size in /etc/fstab as “0” megabytes

It is a bug which can be ignored. Attention is required to be paid if “runcluvfy.sh” and “cluvfy” have different results.

“runcluvfy.sh” pre-check running  shows WARNING about /dev/shm,  but “cluvfy” does not complain.

$ runcluvfy.sh stage  -pre crsinst -n racnode1,racnode2 -verbose
....
...
..
Daemon not running check passed for process "avahi-daemon"

Starting check for /dev/shm mounted as temporary file system ...

WARNING:

The size of in-memory file system mounted at /dev/shm is "259072" megabytes which does not match the size in /etc/fstab as "0" megabytes
The size of in-memory file system mounted at /dev/shm is "259072" megabytes which does not match the size in /etc/fstab as "0" megabytes

Check for /dev/shm mounted as temporary file system passed
....
...
..
.
Pre-check for cluster services setup was unsuccessful on all the nodes.
$cluvfy stage  -pre crsinst -n racnode1,racnode2 -verbose
....
...
..
.
Daemon not running check passed for process "avahi-daemon"
Starting check for /dev/shm mounted as temporary file system ...
Check for /dev/shm mounted as temporary file system passed
Starting check for /boot mount ...
Check for /boot mount passed
Starting check for zeroconf check ...
Check for zeroconf check passed
Pre-check for cluster services setup was successful on all the nodes.

According to Doc (ID 1918620.1) , this WARNING can be ignored.

The size of in-memory file system mounted at /dev/shm is “24576” megabytes which does not match the size in /etc/fstab as “0” megabytes (Doc ID 1918620.1)

 

APPLIES TO:

Oracle Database – Enterprise Edition – Version 12.1.0.2 to 12.1.0.2 [Release 12.1]
Oracle Database – Enterprise Edition – Version 11.2.0.3 to 11.2.0.3 [Release 11.2]
Information in this document applies to any platform.

SYMPTOMS

12.1.0.2 OUI/CVU (cluvfy or runcluvfy.sh) reports the following warning:

WARNING:

The size of in-memory file system mounted at /dev/shm is “24576” megabytes which does not match the
size in /etc/fstab as “0” megabytes

 

OR

 

PRVE-0426 : The size of in-memory file system mounted as /dev/shm is “74158080k” megabytes which is less than the required size of “2048” megabytes on node “”

 

/dev/shm setting is default so no size specified is in /etc/fstab:

$ grep shm /etc/fstab
tmpfs /dev/shm tmpfs defaults 0 0

 

/dev/shm has OS default setting:

$ df -m | grep shm
tmpfs 7975 646 7330 9% /dev/shm

 

CAUSE

Due to unpublished bug 19031737

SOLUTION

Since the size of /dev/shm is bigger than 2GB, the warning can be ignored.

ORA-00845: MEMORY_TARGET not supported on this system

Make sure Oracle Databases are configured by using ASMM, AMM or HUGE PAGES correctly to avoid performance issues.

SYMPTOM

When start up a database, Database failed to be up with ORA-00845 error.

[oracle@racnode1 ~]$ sqlplus /nolog

SQL*Plus: Release 12.1.0.2.0 Production on Sun Mar 15 21:08:17 2015

Copyright (c) 1982, 2014, Oracle. All rights reserved.

SQL> connect / as sysdba
Connected to an idle instance.

SQL> startup
ORA-00845: MEMORY_TARGET not supported on this system

The alert log has messages as below:

Sun Mar 15 21:08:31 2015
WARNING: You are trying to use the MEMORY_TARGET feature. This feature requires the /dev/shm file system to be mounted for at least 1073741824 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 659394560 and used is 499130368 bytes. Ensure that the mount point is /dev/shm for this directory.

SOLUTION

Please confirm that ORACLE_HOME is set correctly. This error sometimes happens when ORACLE_HOME is not set correctly.

Make sure that the /dev/shm size is configured large enough, like in:

# mount -t tmpfs shmfs -o size=2g /dev/shm

In this case, the size of the shared memory device is configured to be 2GB.

In order to make the same change persistent across system reboots, add an entry for this to the /etc/fstab mount table:

shmfs /dev/shm tmpfs size=2g 0 0

NOTE:

  1. You should check with your System Administrator what the “best” size for /dev/shm is, based on what has been reported in the alert file.
  2. Also, many best practices now suggest disabling AMM especially in Exa* Engineered boxes that have larger memory capability, and can use Huge / Large pages.
    This is because AMM and Huge / Large pages are mutually exclusive and overall performance will be better using Huge pages.