Overview

This document explains how to check and configure Linux shared memory settings required for Tibero installation.

Method

1. How to Check Current Settings

# Query shared memory related parameters
$ sysctl kernel.shmmax kernel.shmall kernel.shmmni
kernel.shmmax = 1918869504
kernel.shmall = 468474
kernel.shmmni = 4096

# Check currently created shared memory segments

$ ipcs -m

------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status
0xce389904 2          tibero7    640        1468006400 13

2. Shared Memory Related Parameters

kernel.shmmax : Maximum number of bytes a single shared memory segment can have
kernel.shmall : Total amount of shared memory available system-wide (in number of pages)
kernel.shmmni : Maximum number of shared memory segments (IDs)

kernel.sem = SEMMSL SEMMNS SEMOPM SEMMNI

* SEMMSL: Maximum number of semaphores per semaphore set
* SEMMNS: Maximum number of semaphores system-wide
* SEMOPM: Maximum number of semop operations per call
* SEMMNI: Maximum number of semaphore sets

3. Temporary Application

# Apply immediately
$ sysctl -w kernel.shmmax=17179869184
$ sysctl -w kernel.shmall=4194304
$ sysctl -w kernel.shmmni=4096
$ sysctl -w kernel.sem="1000 32000 100 512"

# Verify changes
$ sysctl kernel.shmmax kernel.shmall kernel.shmmni kernel.sem

* Values reset to those in /etc/sysctl.conf upon OS reboot

4. Permanent Application

* Modify the sysctl.conf file.

$ vi /etc/sysctl.conf
kernel.shmmax = 17179869184     
kernel.shmall = 4194304       
kernel.shmmni = 4096
kernel.sem = 250 32000 100 128

Save after editing

$ sysctl -p

# Verify changes
$ sysctl kernel.shmmax kernel.shmall kernel.shmmni kernel.sem