linux中出现ora27102,关于 ORA-27102: out of memory 解决一例 | YallonKing
问题描述：对内存为24GB的linux 64位之上的oracle11g调整sga大小导致错误ORA-27102，并进一步阐述参数kernel.shmmax和参数kernel.shmall设置问题。
基本信息
OS:linux x86-64 DB:11.2.0.3
[oracle@tongjidb ~]$ more /etc/fstab
#
# /etc/fstab
# Created by anaconda on Fri Nov 1 22:06:11 2013
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=9cf955b0-f18f-4848-90d0-0605663fbab1 / ext4 defaults 1 1
UUID=7d64dc55-51e1-4f9d-89a4-42cbaf6f229a /boot ext4 defaults 1 2
UUID=427C-4136 /boot/efi vfat umask=0077,shortname=winnt 0 0
UUID=66b835cf-0b77-4a2d-bba9-55c821d3215c swap swap defaults 0 0
tmpfs /dev/shm tmpfs defaults,size=20G 0 0
devpts /dev/pts devpts gid=5,mode=620 0 0
sysfs /sys sysfs defaults 0 0
proc /proc proc defaults 0 0
[oracle@tongjidb ~]$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda4 786G 57G 690G 8% /
tmpfs 20G 0 20G 0% /dev/shm
/dev/sda2 3.9G 98M 3.6G 3% /boot
/dev/sda1 3.9G 260K 3.9G 1% /boot/efi
tmpfs 20G 0 20G 0% /dev/shm
[oracle@tongjidb ~]$ free -g
total used free shared buffers cached
Mem: 23 2 20 0 0 2
-/+ buffers/cache: 0 22
Swap: 29 0 29
当前sga设置如下
[root@tongjidb ~]# su - oracle
[oracle@tongjidb ~]$ sqlplus "/as sysdba"
SQL*Plus: Release 11.2.0.3.0 Production on Mon Nov 11 10:30:58 2013
Copyright (c) 1982, 2011, Oracle. All rights reserved.
Connected to:
Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, OLAP, Data Mining and Real Application Testing options
SQL> sho parameter sga
NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
lock_sga boolean FALSE
pre_page_sga boolean FALSE
sga_max_size big integer 7920M
sga_target big integer 7920M
SQL> sho parameter spfile
NAME TYPE
------------------------------------ ----------------------
VALUE
------------------------------
spfile string
/u01/app/oracle/product/11.2.0
/db_1/dbs/spfiletongji.ora
调大sga参数设置，重启数据库报错
SQL> alter system set sga_target=16g scope=spfile;
System altered.
SQL> alter system set sga_max_size=16g scope=spfile;
System altered.
SQL> shutdown immediate;
ORA-01507: database not mounted
ORACLE instance shut down.
SQL> startup nomount;
ORA-27102: out of memory
Linux-x86_64 Error: 28: No space left on device
修改操作系统参数[/etc/sysctl.conf]
#oracle set
fs.aio-max-nr = 1048576
fs.file-max = 6815744
#kernel.shmall = 2097152
kernel.shmall = 5767168
#kernel.shmmax = 4294967295
kernel.shmmax = 23622320128
kernel.shmmni = 4096
kernel.sem = 250 32000 100 128
net.ipv4.ip_local_port_range = 9000 65500
net.core.rmem_default = 262144
net.core.rmem_max = 4194304
net.core.wmem_default = 262144
net.core.wmem_max = 1048586
#oracle set
[root@tongjidb ~]# sysctl -p
参数生效后尝试启动数据库，正常。
SQL> startup nomount;
ORACLE instance started.
Total System Global Area 1.9241E+10 bytes
Fixed Size 2236488 bytes
Variable Size 7247761336 bytes
Database Buffers 1.1945E+10 bytes
Redo Buffers 45682688 bytes
SQL> sho parameter sga
NAME TYPE
------------------------------------ ----------------------
VALUE
------------------------------
lock_sga boolean
FALSE
pre_page_sga boolean
FALSE
sga_max_size big integer
18G
sga_target big integer
18G
参数说明与设定(64位OS)：
kernel.shmmax:
Controls the maximum shared segment size, in bytes
kernel.shmall:
Controls the maximum number of shared memory segments, in pages
[root@tongjidb ~]# getconf PAGE_SIZE
4096
kernel.shmmax 一般为物理内存的一半，最大为物理内存-2GB
我们设置的参数
kernel.shmmax 值为：24GB-2GB=22GB=22*1024*1024*1024=23622320128
kernel.shmall 值为：kernel.shmmax/PAGE_SIZE=23622320128/4096=5767168