AMM, Kernel Parms and tmpfs
I have Oracle Automatic Memory Management running for two oracle databases (one RAC and one single instance). The setup below:
RAC (3 node)
OEL 5u2
Oracle Clusterware 11.2.0.2
Oracle ASM 11.2.0.2
Oracle RDBMS 11.2.0.2
Single Instance
OEL 5u2
Oracle Restart 11.2.0.2
Oracle ASM 11.2.0.2
Oracle RDBMS 11.2.0.2
We just upgraded the memory for both RAC and SI servers from 8GB to 16 GB. I wanted to adjust several parameters to accomodate the added memory. I used the following setup:
shmall = 3670016
shmmax = 15032385535
Note: 14 GB – 1 byte
Shared Memory (tmpfs)
/dev/shm = 14 GB
memory_target=15032385535
Note: 14G - 1 byte
tmpfs 14680064 4546512 10133552 31% /dev/shm
I am getting the "ORA-00845: MEMORY_TARGET not supported on this system" error. How come I can increase shmall and /dev/shm to 16 GB and it works? Or, reduce MEMORY_TARGET to 13 GB in the listed configuration and it works.
Please confirm my understanding, the MEMORY_TARGET accommodates all SGA and PGA. The dynamic memory allocation is handled in OEL with Shared Memory. The SHMMAX establishes the largest allocated segment of shared memory. Setting SHMMAX and MEMORY_TARGET equal ensures entire SGA and PGA will be in one Shared Memory Segment. The SHMALL is the total shared memory possible. The tmpfs is the physical file system mapped to shared memory so tmpfs must be as large as SHMALL. I've seen articles that say SHMMAX should be sized to the largest SGA size. Given that MEMORY_TARGET now accomodates both SGA and PGA, this seemed wrong.
Under this understanding, if SHMALL and tmpfs are equal and the SHMMAX and MEMORY_TARGET are less than SHMALL and tmpfs then the ORA-00845 shouldn't occur. Since my configuration doesn't work, I am assuming that something in my understanding is wrong and I need to accommodate more space between total shared memory and the MEMORY_TARGET. please explain.