Configuring Kernel Parameters

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Note: The kernel parameter and shell limit values shown in the following section are recommended values only.

For production database systems, Oracle recommends that you tune these values to optimize the performance of the system.

Refer to your operating system documentation for more information about tuning kernel parameters.

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Verify that the kernel parameters shown in the following table are set to values greater than or equal to the recommended value shown.

The procedure following the table describes how to verify and set the values.

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Parameter                                                 Value                                        File
semmsl                                                         250                                          /proc/sys/kernel/sem
semmns                                                      32000
semopm                                                      100

semmni                                                       128

............................................................................................................................................................................................

shmall                                                    2097152                                        /proc/sys/kernel/shmall

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shmmax                         Half the size of physical memory (in bytes)              /proc/sys/kernel/shmmax

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shmmni                                                 4096                                              /proc/sys/kernel/shmmni

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file-max                                                65536                                            /proc/sys/fs/file-max

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ip_local_port_range       Minimum:1024 Maximum: 65000                          /proc/sys/net/ipv4/ip_local_port_range

..............................................................................................................................................................................................

rmem_default                                     1048576                                          /proc/sys/net/core/rmem_default

...............................................................................................................................................................................................

rmem_max                                        1048576                                           /proc/sys/net/core/rmem_max

...............................................................................................................................................................................................

wmem_default                                   262144                                             /proc/sys/net/core/wmem_default

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wmem_max                                       262144                                            /proc/sys/net/core/wmem_max

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Note:

If the current value for any parameter is higher than the value listed in this table, then do not change the value of that parameter.

 

To view the current value specified for these kernel parameters, and to change them if necessary:
1. Enter the commands shown in the following table to view the current values of the kernel parameters:

Note:

Make a note of the current values and identify any values that you must change.

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Parameter                                                          Command

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semmsl, semmns,                                                   # /sbin/sysctl -a | grep sem
semopm, and semmni                           This command displays the value of the semaphore parameters in the order listed. 

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shmall, shmmax, and  shmmni                                # /sbin/sysctl -a | grep shm

                                                            This command displays the details of the shared memory segment sizes.

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file-max                                                                # /sbin/sysctl -a | grep file-max
                                                            This command displays the maximum number of file handles.

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ip_local_port_range                                             # /sbin/sysctl -a | grep ip_local_port_range
                                                            This command displays a range of port numbers.

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rmem_default                                                      # /sbin/sysctl -a | grep rmem_default

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rmem_max                                                         # /sbin/sysctl -a | grep rmem_max

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wmem_default                                                   # /sbin/sysctl -a | grep wmem_default

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wmem_max                                                       # /sbin/sysctl -a | grep wmem_max

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2. If the value of any kernel parameter is different from the recommended value,then complete the following procedure:
Using any text editor, create or edit the /etc/sysctl.conf file, and add or edit lines similar to the following:

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Note:

Include lines only for the kernel parameter values that you want to change.

For the semaphore parameters (kernel.sem), you must specify all four values.

However, if any of the current values are larger than the recommended value, then specify the larger value.

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kernel.shmall = 2097152
kernel.shmmax = 2147483648
kernel.shmmni = 4096
kernel.sem = 250 32000 100 128
fs.file-max = 65536
net.ipv4.ip_local_port_range = 1024 65000
net.core.rmem_default = 1048576
net.core.rmem_max = 1048576
net.core.wmem_default = 262144
net.core.wmem_max = 262144

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By specifying the values in the /etc/sysctl.conf file, they persist when you restart the system.----->sysctl -p這個(gè)命令在這里可以有效果嗎，待驗(yàn)證。