如何避免SGA和PGA的大量交换？
Oracle 11g中增加了AMM，在使用过程中发现总是会发生SGA和PGA大量交换，可以怎么避免？再修改为ASMM时发生ORA-00845，是什么原因？
3同行回答
官网上有这个解析的
官方解析
Starting with Oracle Database 11g, the Automatic Memory Management feature requires more shared memory (/dev/shm)and file descriptors. The size of the shared memory should be at least the greater of MEMORY_MAX_TARGET and MEMORY_TARGET for each Oracle instance on the computer. If MEMORY_MAX_TARGET or MEMORY_TARGET is set to a non zero value, and an incorrect size is assigned to the shared memory, it will result in an ORA-00845 error at startup.
解决问题建议
If you are installing Oracle 11g on a Linux system, note that Memory Size (SGA and PGA), which sets the initialization parameter MEMORY_TARGET or MEMORY_MAX_TARGET, cannot be greater than the shared memory filesystem (/dev/shm) on your operating system. To resolve the current error, increase the /dev/shm file size.
If configuring AMM is not possible due to lack of space on /dev/shm mount point, you can configure ASMM instead of AMM, i.e. set SGA_TARGET, SGA_MAX_SIZE and PGA_AGGREGATE_TARGET instead of MEMORY_TARGET.收起
官方解析
Starting with Oracle Database 11g, the Automatic Memory Management feature requires more shared memory (/dev/shm)and file descriptors. The size of the shared memory should be at least the greater of MEMORY_MAX_TARGET and MEMORY_TARGET for each Oracle instance on the computer. If MEMORY_MAX_TARGET or MEMORY_TARGET is set to a non zero value, and an incorrect size is assigned to the shared memory, it will result in an ORA-00845 error at startup.
解决问题建议
If you are installing Oracle 11g on a Linux system, note that Memory Size (SGA and PGA), which sets the initialization parameter MEMORY_TARGET or MEMORY_MAX_TARGET, cannot be greater than the shared memory filesystem (/dev/shm) on your operating system. To resolve the current error, increase the /dev/shm file size.
If configuring AMM is not possible due to lack of space on /dev/shm mount point, you can configure ASMM instead of AMM, i.e. set SGA_TARGET, SGA_MAX_SIZE and PGA_AGGREGATE_TARGET instead of MEMORY_TARGET.收起
浏览1479
发生这个问题的原因可以是因为主机上面的内存参数设的小了
/dev/shm 太小
根本的原因就是修改asmm失败了
startup
ORA-00845: MEMORY_TARGET not supported on this system
因为我一个库里有两个实例，启动时/dev/shm就不够用了。
在Oracle 11g中如果采用AMM内存管理，那么当MEMORY_TARGET的值大于/dev/shm的时候，就会报ORA-00845: MEMORY_TARGET not supported on this system错误，解决办法增加/dev/shm大小，在redhat系列系统中，/dev/shm的默认值是系统总内存的一半收起
/dev/shm 太小
根本的原因就是修改asmm失败了
startup
ORA-00845: MEMORY_TARGET not supported on this system
因为我一个库里有两个实例，启动时/dev/shm就不够用了。
在Oracle 11g中如果采用AMM内存管理，那么当MEMORY_TARGET的值大于/dev/shm的时候，就会报ORA-00845: MEMORY_TARGET not supported on this system错误，解决办法增加/dev/shm大小，在redhat系列系统中，/dev/shm的默认值是系统总内存的一半收起
浏览1385
在OS中有控制类似SHMMAX这样的kernel,这个设置过小将会使得内存一部分给换出到磁盘，一般设置为物理内存的80%合适收起
浏览1367