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Purpose

To explain differences between semget and shmget

Overview

Mind the differences: shmget vs. semget. How to avoid?

Mind the differences: shmget vs. semget

  • shmget: points to shared memory
  • semget: points to semaphore

How to avoid?

Case A: SHMGET

When starting the SAP system following error appears in dev_wxx trace:

  • ERROR => e=28 shmget(...) (28: No space left on device)
    ===> lack of shared memory resources
  • ERROR => shmget(...) (28: No space left on device)
    ===> lack of semaphore resources

Check the OS configuration:

Linux

kernel.shmmax in /etc/sysctl.conf. Activate changes by 'sysctl -p'. 
If the parameter apprer more than once there comment out the lower one by #, like:

 > cat /etc/sysctl.conf | grep shm
kernel.shmmax = 68719476736
kernel.shmall = 41943040
#kernel.shmmax=23136829430   <<<--- this
#kernel.shmall=5242880   <<<--- and this

Oracle Solaris

process.max-shm-memory (as of Solaris 10)

Case B: SEMGET

When starting the SAP system following error appears in dev_wxx trace:

  • ERROR => e=28 semget(...) (28: No space left on device)
  • ERROR => semget(...) (28: No space left on device)

Check the OS configuration:

Linux

kernel.sem in /etc/sysctl.conf. Activate changes by 'sysctl -p'.

For SLES, the sapconf/saptune will configure high enough values for kernel.sem

Oracle Solaris

process.max-sem-nsems (as of Solaris 10)

In every case: Restart both SAP Start Service (sapstartsrv) process and SAP system to activate changes on SAP level !

Related Content

Related Documents

System Administration Guide: Oracle Solaris Containers-Resource Management and Oracle Solaris Zones

Related SAP Notes/KBAs

SAP Note 724713: Parameter Settings for Oracle Solaris 10 and above
SAP Note 1275776: Linux: Preparing SLES for SAP environments
SAP Note 722273: Red Hat Enterprise Linux 3.x, 4.x: Installation and Upgrade
SAP Note 1496410 - Red Hat Enterprise Linux 6.x: Installation and Upgrade
SAP Note 2002167 - Red Hat Enterprise Linux 7.x: Installation and Upgrade
SAP Note 1635808 - Oracle Linux 6.x SAP Installation and Upgrade
SAP Note 2069760 - Oracle Linux 7.x SAP Installation and Upgrade
SAP KBA 1584228: Internal error in secure store/Semaphore run out on a system

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