FAQ : 系统内核参数shmmax太小问题

问题描述：

查看日志显示：

2022-10-10 17:22:07.404 6343e43f.1 [unknown] 140589512277056 [unknown] 0 dn1 42809 0 [BACKEND] DETAIL: Failed system call was shmget(key=15432001, size=4673011712, 03600).

2022-10-10 17:22:07.404 6343e43f.1 [unknown] 140589512277056 [unknown] 0 dn1 42809 0 [BACKEND] HINT: This error usually means that openGauss's request for a shared memory segment exceeded your kernel's SHMMAX parameter. You can either reduce the request size or reconfigure the kernel with larger SHMMAX. To reduce the request size (currently 4673011712 bytes), reduce openGauss's shared memory usage, perhaps by reducing shared_buffers.

 If the request size is already small, it's possible that it is less than your kernel's SHMMIN parameter, in which case raising the request size or reconfiguring SHMMIN is called for.

 The openGauss documentation contains more information about shared memory configuration.

解决方法：

修改shmmax内核参数，使SGA存在于一个共享内存段中。通过修改/proc/sys/kernel/shmmax参数可以达到此目的。

echo 140589512277056> /proc/sys/kernel/shmmax

对于shmmax文件的修改，系统重新启动后会复位。可以通过修改/etc/sysctl.conf使更改永久化。在该文件内添加以下一行 kernel.shmmax = 140589512277056。这个更改在系统重新启动后生效。