Setting Kernel Parameters in Linux during ORACLE Installation

A Redhat official ORACLE Installation document is displayed two days ago when you set Kernel Parameters in Linux. The modification description of Linux kernel parameters is very clear. Before installing Oracle, in addition to checking whether the hardware and software of the operating system meet the installation requirements, the key is to modify the kernel parameters, the most important of which is the memory-related parameter settings. Parameter www.2cto.com SHMMAX: maximum value of the separately shared memory segment that can be allocated by a Linux Process. It is generally set to half the total memory size. The setting of this value should be greater than the value of SGA_MAX_TARGET or MEMORY_MAX_TARGET. Therefore, the shmmax value of the system that installs the Oracle database should be larger than 1/2 of the memory. # Grep MemTotal/proc/meminfo # The command above cat/proc/sys/kernel/shmmax checks the system memory size and the current shmmax settings. # Echo 21474836480>/proc/sys/kernetbl/shmmax # sysctl-w kernel. shmmax = 21474836480 # echo "kernel. shmmax = 21474836480 ">/etc/sysctl. conf: several methods for setting the shmmax parameter. You can set shmmax to 20 GB in either of the three methods. You can modify this parameter without restarting the database. We recommend that you use the second sysctl command. The third method requires the sysctl-t operation or restart. However, the third method is essential to ensure that the setting value remains effective after the next restart. The first two methods are similar to alter system set scope = memory, while the third method is similar to alter system set scope = spfile. SHMMNI parameter: set the maximum number of system-level shared memory segments. We recommend that you set the minimum value of Oracle10g to 4096, which can be increased by 4096. Www.2cto.com # cat/proc/sys/kernel/shmmni # echo 4096>/proc/sys/kernel/shmmni # sysctl-w kernel. shmmni = 4096 # echo "kernel. shmmni = 4096 ">/etc/sysctl. the conf check and setting method are as follows. This is no different from the shmmax modification method. SHMALL parameter: Set the total number of pages in the shared memory. If the value is too small, an error may be reported during database startup. Many people only pay attention to the SHMMAX parameter when adjusting system kernel parameters, but ignore the SHMALL parameter settings. The recommended value is physical memory size divided by page size. # Getconf PAGE_SIZE: Get the page size through getconf to calculate the reasonable SHMALL setting value: SQL> select 32*1024*1024*1024/4096 from dual; 32*1024*1024*1024/4096 -------------------- 8388608 www.2cto.com for 32 GB memory, 4 K paging system, SHMALL value should be set to 8388608. # Cat/proc/sys/kernel/shmall # echo 8388608>/proc/sys/kernel/shmall # sysctl-w kernel. shmall = 8388608 # echo "kernel. shmall = 8388608 ">/etc/sysctl. the conf query and setting methods are as follows. Semaphores is a counter that provides synchronization when processes or threads access shared memory. SEMMSL parameter: sets the maximum number of signals in each traffic signal group. The recommended minimum value is 250. For systems with a large number of concurrent connections, we recommend that you set this value to the PROCESSES initialization parameter plus 10. SEMMNI parameter: set the maximum number of traffic signal groups in the system. The recommended Oracle10g and 11g values are 142. SEMMNS parameter: set the maximum number of signals in the system. The OS does not exceed LEAST (SEMMNS, SEMMSL * SEMMNI) when allocating traffic signals ). In fact, if the SEMMNS value exceeds SEMMSL * SEMMNI, it is invalid. Therefore, we recommend that you set the SEMMNS value to SEMMSL * SEMMNI. The recommended SEMMNS setting in Oracle is no less than 32000. If the PROCESSES parameter of the database is set to 600, SEMMNS should be set to SQL> select (600 + 10) * 142 from dual; www.2cto.com (600 + 10) * 142 ------------ 86620 SEMOPM parameter: set the maximum number of traffic signal operations that can be performed simultaneously by each system call. Because a traffic signal group can have a maximum of SEMMSL traffic signals, we recommend that you set SEMOPM to SEMMSL. The SEMOPM configurations for Oracle 10.2 and 11.1 are 100. Run the following command to check the traffic signal Configuration: # The four values of cat/proc/sys/kernel/sem250 32000 100 128 are respectively SEMMSL, SEMMNS, SEMOPM, and SEMMNI from left to right. Modification Method: # echo 610 86620 100 142>/proc/sys/kernel/sem # sysctl-w kernel. sem = "610 86620 100 142" # echo "kernel. sem = 610 86620 100 142 ">/etc/sysctl. conf