Configuring Very Large Memory (VLM)
61
use_indirect_data_buffers=true
db_block_size=8192
db_block_buffers=1048576
shared_pool_size=2831155200
Note that
shmmax
needs to be increased for
shared_pool_size
to fit into the System V shared
memory. In fact, it should be slightly larger than the SGA size. Since
shared_pool_size
is less than
3 GB in this example,
shmmax
does not need to be larger than 3GB. The 8 GB indirect buffer cache
will be in the RAM disk and hence it does not have to be accounted for in
shmmax
. On a 32 bit system
the
shmmax
kernel parameter cannot be larger than 4GB, see also
Section 7.3, “Setting SHMALL
Parameter”
.
In order to allow oracle processes to lock more memory into its address space for the VLM window
size, the
ulimit
parameter
memlock
must be changed for oracle. Ensure to set
memlock
in
/etc/
security/limits.conf
to 3145728:
oracle soft memlock 3145728
oracle hard memlock 3145728
Login as Oracle again and check max locked memory limit:
$ ulimit -l
3145728
If it is not working after a
ssh
log in, then you may have to set the SSH parameter
UsePrivilegeSeparation
, see
Chapter 22, Setting Shell Limits for Your Oracle User
.
If
memlock
is not set or too small, you will get error messages similar to this one:
ORA-27103: internal error
Linux Error: 11: Resource temporarily unavailable
Now try to start the database. Note the database start up can take a while. Also, the
sqlplus
banner
or show sga may not accurately reflect the actual SGA size in older Oracle versions.
The 8GB file for the database buffer cache can be seen in the ramfs shared memory file system:
$ ls -al /dev/shm
total 120
drwxr-xr-x 1 oracle dba 0 Nov 20 16:29 .
drwxr-xr-x 22 root root 118784 Nov 20 16:25 ..
-rw-r----- 1 oracle dba 8589934592 Nov 20 16:30 ora_orcl_458754
$
If the shared pool size is configured too large, you will get error messages similar to this one:
ORA-27103: internal error
Linux Error: 12: Cannot allocate memory
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