Oracle因开启大页内存无法启动ORA-27100: shared memory realm already exists Linux-x86_64 Error: 17: File exists

测试环境版本信息：
[root@sourcedb ~]# cat /etc/redhat-release 
Red Hat Enterprise Linux Server release 6.5 (Santiago)
[root@sourcedb ~]# su - oracle
[oracle@sourcedb ~]$ sqlplus 
SQL*Plus: Release 11.2.0.4.0 Production on Fri Apr 14 07:12:04 2017
Copyright (c) 1982, 2013, Oracle.  All rights reserved.


[root@sourcedb ~]# free -m
             total       used       free     shared    buffers     cached
Mem:           988        472        515          0          0         23
-/+ buffers/cache:        448        540
Swap:         2047        265       1782
[root@sourcedb ~]# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        38G   13G   24G  35% /
tmpfs           495M   72K  495M   1% /dev/shm
/dev/sda1       194M   30M  155M  16% /boot




根据Oracle开启大页内存的方式，在/etc/sysctl.conf中添加如下参数：
vm.nr_hugepages = 180
[root@sourcedb ~]# sysctl -p   使该参数生效。


此时启动数据库报错如下：
SQL> startup nomount
ORA-27100: shared memory realm already exists
Linux-x86_64 Error: 17: File exists
Additional information: 2097152


alert日志输出如下：
********************************************************************
Fri Apr 14 07:11:06 2017
Starting ORACLE instance (normal)




在/etc/sysctl.conf中注释掉大页内存参数：
[root@sourcedb ~]# cat /etc/sysctl.conf 
...
#vm.nr_hugepages = 180
...


[root@sourcedb ~]# sysctl -p




再次启动数据库正常：
SQL> startup nomount
ORACLE instance started.


Total System Global Area  367439872 bytes
Fixed Size                  2253344 bytes
Variable Size             171970016 bytes
Database Buffers          188743680 bytes
Redo Buffers                4472832 bytes
SQL> alter database mount;


Database altered.


SQL> alter database open;


Database altered.