Home > oracle_init_parameters > Configuring Linux Hugepages for Oracle Database

Configuring Linux Hugepages for Oracle Database

In this article we are going to discuss setting up hugapages on linux and using it for oracle instance.

*dbslcert*:/home/oracle/admin/diag/rdbms/oradv1/oradv1/trace=>grep Huge /proc/meminfo
HugePages_Total: 0
HugePages_Free: 0
HugePages_Rsvd: 0
Hugepagesize: 2048 kB

Each huge page size is 2MB and for 512MB sga we need 256 huge pages.

Add following entry in /etc/sysctl.conf and reboot the system.

I am adding only 160 pages and will test different scenarios by using init.ora file to start oracle instance.
vm.nr_hugepages = 160

cat /proc/meminfo
HugePages_Total: 160
HugePages_Free: 160
HugePages_Rsvd: 0
Hugepagesize: 2048 kB

Scenario 1:

Hugepages is not support with AMM

use_large_pages=only
memory_max_target=800M
memory_target=800M

SQL> HOST date
Wed Apr 20 21:44:35 PDT 2011

SQL> startup force pfile=./initoradv1.ora
ORA-27125: unable to create shared memory segment
Linux-x86_64 Error: 2: No such file or directory

Error:

Wed Apr 20 21:40:44 2011
Starting ORACLE instance (normal)
******************************************************************
Huge Pages are not compatible with specified SGA memory parameters
use_large_pages = “ONLY” cannot be used with memory_target,
memory_max_target, or use_indirect_data_buffers parameters
Huge Pages are compatible with sga_target and shared_pool_size

scenario 2:

AMM is disabled by setting memory_max_target = 0
Starting ORACLE instance (normal)
****************** Huge Pages Information *****************
Huge Pages memory pool detected (total: 160 free: 160)
Huge Pages allocation failed (free: 160 required: 257)
Startup will fail as use_large_pages is set to “ONLY”
******************************************************
Summary:

use_large_pages is a must-set parameter if we need hugepages. With initialization parameters like use_large_pages, configuring hugepages for Oracle Database is very easy.

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