1、检查memory_target，memory_max_target，如果不为0，将其更改为0.

SQL> show parameter memory_target

NAME TYPE VALUE

------------------------------------ ----------- ------------------------------

memory_target big integer 0

SQL> show parameter memory_max_target

NAME TYPE VALUE

------------------------------------ ----------- ------------------------------

memory_max_target big integer 0

SQL>

2、计算hugepages的值（脚本内容见最后）

[root@gxjzfpdb01 soft]# ./hugepages_settings.sh

This script is provided by Doc ID 401749.1 from My Oracle Support

(http://support.oracle.com) where it is intended to compute values for

the recommended HugePages/HugeTLB configuration for the current shared

memory segments. Before proceeding with the execution please make sure

that:

* Oracle Database instance(s) are up and running

* Oracle Database 11g Automatic Memory Management (AMM) is not setup

(See Doc ID 749851.1)

* The shared memory segments can be listed by command:

# ipcs -m

Press Enter to proceed...

Recommended setting: vm.nr_hugepages = 19012

得出大页的大小为19012页（注：一页为2M，这个值不可改，19012*2M=38024M），实际上hugepages与参数sga_max_size有关，比sga_max_size的值稍微大一点点（比SGA_MAX_SIZE最少要多加一页，2M的页不要分配超过sga_max_size太多，会造成内存的浪费）：

SQL> show parameter sga

NAME TYPE VALUE

------------------------------------ ----------- ------------------------------

lock_sga boolean FALSE

pre_page_sga boolean FALSE

sga_max_size big integer 38016M

sga_target big integer 38016M

3、设置hugepages，在内核参数中添加一行,vi /etc/sysctl.conf

vm.nr_hugepages = 19012

4、修改内核参数立即生效
[root@gxjzfpdb01 ~]# sysctl -p

5、设定/etc/security/limits.conf文件，以K为单位，必须大于sga_max_size,这里设定为89128960

[root@gxjzfpdb01 ~]# vi /etc/security/limits.conf

* soft memlock 89128960

* hard memlock 89128960

6、检查limits是否正确
[root@gxjzfpdb01 ~]# su - oracle
[oracle@gxjzfpdb02 ~]$ ulimit -l

89128960

7、重启数据库，检查大页是否被使用。

SQL> shu immediate

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> exit

Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production

With the Partitioning, Real Application Clusters, Automatic Storage Management, OLAP,

Data Mining and Real Application Testing options

[oracle@gxjzfpdb02 ~]$ exit

logout

[root@gxjzfpdb02 ~]# su - oracle

[oracle@gxjzfpdb02 ~]$ sqlplus / as sysdba

SQL*Plus: Release 11.2.0.4.0 Production on Mon Jun 6 11:40:56 2016

Connected to an idle instance.

SQL> startup

ORACLE instance started.

Total System Global Area 3.9685E+10 bytes

Fixed Size 2261728 bytes

Variable Size 6576672032 bytes

Database Buffers 3.3018E+10 bytes

Redo Buffers 88203264 bytes

Database mounted.

Database opened.

SQL>

检查大页特性是否使用：

[root@gxjzfpdb02 soft]# cat /proc/meminfo | grep Hu

AnonHugePages: 342016 kB

HugePages_Total: 19012

HugePages_Free: 15157

HugePages_Rsvd: 15154

HugePages_Surp: 0

Hugepagesize: 2048 kB

[root@gxjzfpdb02 soft]#

注：
HugePages_Total: 19012---总共1028页
HugePages_Free: 15157---空闲15157页，即当前大页被使用了19012-15157=3855页，即被用了3855*2M=7710M，小于sga_target。
HugePages_Rsvd: 15154---操作系统承诺给Oracle预留15154页，即15154*2M=30308M（30308+7710==SGA_MAX_SIZE）
Hugepagesize: 2048 kB --每页是2M，不可修改

可以看到，大页已被使用，至此，大页特性已经开启。

附脚本内容：
#!/bin/bash
#
# hugepages_settings.sh
#
# Linux bash script to compute values for the
# recommended HugePages/HugeTLB configuration
#
# Note: This script does calculation for all shared memory
# segments available when the script is run, no matter it
# is an Oracle RDBMS shared memory segment or not.
#
# This script is provided by Doc ID 401749.1 from My Oracle Support
# http://support.oracle.com

# Welcome text
echo "
This script is provided by Doc ID 401749.1 from My Oracle Support
(http://support.oracle.com) where it is intended to compute values for
the recommended HugePages/HugeTLB configuration for the current shared
memory segments. Before proceeding with the execution please make sure
that:
* Oracle Database instance(s) are up and running
* Oracle Database 11g Automatic Memory Management (AMM) is not setup
(See Doc ID 749851.1)
* The shared memory segments can be listed by command:
# ipcs -m

Press Enter to proceed..."

read

# Check for the kernel version
KERN=`uname -r | awk -F. '{ printf("%d.%d\n",$1,$2); }'`

# Find out the HugePage size
HPG_SZ=`grep Hugepagesize /proc/meminfo | awk '{print $2}'`

# Initialize the counter
NUM_PG=0

# Cumulative number of pages required to handle the running shared memory segments
for SEG_BYTES in `ipcs -m | awk '{print $5}' | grep "[0-9][0-9]*"`
do
MIN_PG=`echo "$SEG_BYTES/($HPG_SZ*1024)" | bc -q`
if [ $MIN_PG -gt 0 ]; then
NUM_PG=`echo "$NUM_PG+$MIN_PG+1" | bc -q`
fi
done

RES_BYTES=`echo "$NUM_PG * $HPG_SZ * 1024" | bc -q`

# An SGA less than 100MB does not make sense
# Bail out if that is the case
if [ $RES_BYTES -lt 100000000 ]; then
echo "***********"
echo "** ERROR **"
echo "***********"
echo "Sorry! There are not enough total of shared memory segments allocated for
HugePages configuration. HugePages can only be used for shared memory segments
that you can list by command:

# ipcs -m

of a size that can match an Oracle Database SGA. Please make sure that:
* Oracle Database instance is up and running
* Oracle Database 11g Automatic Memory Management (AMM) is not configured"
exit 1
fi

# Finish with results
case $KERN in
'2.4') HUGETLB_POOL=`echo "$NUM_PG*$HPG_SZ/1024" | bc -q`;
echo "Recommended setting: vm.hugetlb_pool = $HUGETLB_POOL" ;;
'2.6') echo "Recommended setting: vm.nr_hugepages = $NUM_PG" ;;
*) echo "Unrecognized kernel version $KERN. Exiting." ;;
esac

# End

Oracle数据库在linux平台上开启大页特性