/dev/shm on Oracle Linux 6.x to run Oracle 11g R2 - manual configuration?

Question

Hello
We are building a server to run Oracle 11g R2 database (11.2.0.3 x64) on Oracle Linux 6.2 with UEK R2.
Our preference is to use AMM to have Oracle 11g R2 manage memory. We may impose some minium SGA and PGA memory allocations but basically aim to use MEMORY_TARGET to manage overall memory.
By default Linux makes the size of /dev/shm ~50% of server physical RAM, as far as I can tell.
Here is the /etc/fstab entry created by the installation:
tmpfs /dev/shm tmpfs defaults 0 0
Given this Linux server will only run Oracle 11g R2 database and some monitoring software, almost application code will run on the server. The application code will run on the separate application server and is Java based.
Can I change the */etc/fstab* entry for /dev/shm to manually increase the size to take up ~80-90% of the server physical RAM ? Is it a good idea?
The server is 64-bit, the RAM = 64 GB, so I am thinking to manually make /dev/shm to be = ~55GB, leaving ~8GB for other purposes.
Right now it's about 32GB (50%?) if I leave the /dev/shm 'defaults' on.
many thanks

Answer 1

thanks,
I have read the doc (what little there is on this topic).
I have asked on the database forum......
just FYI - below is the proof:
SQL> show parameter mem
NAME                    TYPE     VALUE
hi_shared_memory_address     integer     0
memory_max_target          big integer 4G
memory_target          big integer 0
shared_memory_address     integer     0
SQL> show parameter ga
NAME                    TYPE     VALUE
lock_sga               boolean     FALSE
pga_aggregate_target          big integer 1600M
pre_page_sga          boolean     FALSE
sga_max_size          big integer 3G
sga_target               big integer 1600M
still does not work.
And I cant change memory_max_target = 0 because I get error on startup:
SQL> alter system set memory_max_target=0 scope=spfile;
System altered.
SQL> shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup;
ORA-01078: failure in processing system parameters
ORA-00843: Parameter not taking MEMORY_MAX_TARGET into account
ORA-00849: SGA_TARGET 3221225472 cannot be set to more than MEMORY_MAX_TARGET 0.
BUT if memory_max_target is > 0 then alert log says hugepages can not be used
it feels like catch-22.....
thanks
Edited by: yurib on Jun 1, 2012 4:53 PM