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During the installation of the database on the linux system, it involves setting linux kernel parameters

Kernel.shmall = 2097152 # the total amount of shared memory available, in pages.

Kernel.shmmax = 2147483648 # maximum size of a single shared memory segment. Take half of the physical memory size in bytes

Kernel.shmmni = 4096 # the maximum number of shared memory segments for the entire system.

Kernel.sem = 32000 100128 # the maximum number of signal objects per signal object set; the maximum number of signal objects in the system scope; the maximum number of operands supported by each signal object; the maximum number of signal object sets in the system scope.

Fs.file-max = 65536 # the maximum number of file handles allowed in the system.

Net.ipv4.ip_local_port_range = 1024 65000 # range of IPv4 ports that can be used by applications.

Net.core.rmem_default = 1048576 # default value of socket receive buffer size

Net.core.rmem_max = 1048576 # maximum size of socket receive buffer size

Net.core.wmem_default = 262144 # default value of socket send buffer size

Net.core.wmem_max = 262144 # maximum size of socket send buffer size

Shared memory:

You can view the parameter limits of the current system shared memory through the ipcs-lm command:

# ipcs-lm

-Shared Memory Limits-

Max number of segments = 4096

Max seg size (kbytes) = 1048576

Max total shared memory (pages) = 2097152

Min seg size (bytes) = 1

Here are three parameters related to shared memory: SHMMAX,SHMMNI,SHMALL

SHMMAX

Meaning: maximum number of bytes per shared memory segment

Setting: slightly larger than SGA

View: cat / proc/sys/kernel/shmmax

$cat / proc/sys/kernel/shmmax

1073741824

Modify:

Sysctl-w kernel.shmmax=1073741824

Echo "kernel.shmmax=1073741824" > > / etc/sysctl.conf

SHMMNI

Meaning: maximum number of shared memory segments

Setting: at least 4096

View: cat / proc/sys/kernel/shmmni

# cat / proc/sys/kernel/shmmni

4096

Modify:

# sysctl-w kernel.shmmni=4096

# echo "kernel.shmmni=4096" > > / etc/sysctl.conf

SHMALL

Meaning: total number of shared memory pages in the system

Setting: at least ceil (shmmax/PAGE_SIZE); ORACLE DOC default: 2097152*4096=8GB

View: cat / proc/sys/kernel/shmall

$getconf PAGE_SIZE

4096

# cat / proc/sys/kernel/shmall

2097152

Modify:

# sysctl-w kernel.shmall=2097152

# echo "kernel.shmall=2097152" > > / etc/sysctl.conf

Semaphore:

Current system semaphore limits:

Oracle@lab-rd-01:~$ ipcs-ls

-Semaphore Limits-

Max number of arrays = 128,

Max semaphores per array = 250

Max semaphores system wide = 32000

Max ops per semop call = 100

SEMMSL

Meaning: the maximum number of semaphores in each semaphore set

Setting: minimum 250; for systems with large processes parameter setting, it is recommended to set it to processes+10

SEMMNI

Meaning: the maximum number of semaphores set in linux system

Setting: at least 128

SEMMNS

Meaning: the maximum number of semaphores in linux system

Setting: at least 32000 position SEMMSL * SEMMNI

SEMOPM

Meaning: the maximum number of semaphores allowed for semop system calls

Setting: at least 100; or equal to SEMMSL

View semaphore settings: cat / proc/sys/kernel/sem

Order:SEMMSL, SEMMNS, SEMOPM, SEMMNI

Oracle@lab-rd-01:~$ cat / proc/sys/kernel/sem

250 32000 100 128

Modify:

Sysctl-w kernel.sem= "250 32000 100128"

Echo "kernel.sem=250 32000 100128" > > / etc/sysctl.conf

ORACLE provides sysresv tools to manage shared memory and semaphores, and the operating system level can be managed through ipcs.

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