MEMORY_MAX_TARGET and relationship with SHMMA & /dev/shm
Hello.
We are wanting to use Automated Memory Mgmt (AMM) and know that the sizing of the init parms of MEMORY_MAX_TARGET/MEMORY_TARGET must fit within the size of the /dev/shm mount point. We have 16G of memory on each of our 11g RAC DB servers. I realize that the Linux OS needs a good chunk of this memory and I also realize that the Oracle 11g Install documentations indicates that the sizing the shmmax parameter = the minimum of (4GB - 1 byte), or half the size of physical memory (in bytes), whichever is lower. IN our case, the 4G IS the LOWER limit, so we will use it.
Here's my question and it is based on the fact that we have 16G of memory on each of our DB servers.
1.) If we set the MEMORY_MAX_TARGET/MEMORY_TARGET parameters =4G, shouldn't we also size BOTH shmmax and /dev/shm also = 4G?
My other 2 are more general as I am not an SA.
2.) Should shmmax and /dev/mnt always be the same size?
3.) If we set SHMMAX and /dev/shm to 4G, does the remaining 12G on each of our DB servers get used entirely by the OS? Seems like we really don't get to use the full memory capacity of these servers when we only get to allocate 4G of it to the DB.
Thank you in advance for any/all comments.
Matt