ORA-00845 1

mysql oracle 关于
oracle 11g ORA-00845 处理方法一则
[oracle@db11g ~]$ sqlplus “/as sysdba”

SQL*Plus: Release 11.2.0.1.0 Production on Mon Jul 11 12:52:21 2011

Copyright (c) 1982, 2009, Oracle. All rights reserved.

Connected to an idle instance.

SQL> startup
ORA-00845: MEMORY_TARGET not supported on this system

查看alert文件的提示：
Starting ORACLE instance (normal)
WARNING: You are trying to use the MEMORY_TARGET feature. This feature requires the /dev/shm file system to be mounted for at least 2046820352 bytes.

/dev/shm is either not mounted or is mounted with available space less than this size. Please fix this so that MEMORY_TARGET can work as expected. Current

available is 1989042176 and used is 0 bytes. Ensure that the mount point is /dev/shm for this directory.
memory_target needs larger /dev/shm
Mon Jul 11 12:52:22 2011

根据oracle参考手册上对ora-00845的解释:

ORA-00845: MEMORY_TARGET not supported on this system
Cause: The MEMORY_TARGET parameter was not supported on this operating system or /dev/shm was not sized correctly on Linux.
Action: Refer to documentation for a list of supported operating systems. Or, size /dev/shm to be at least the SGA_MAX_SIZE on each Oracle instance running

on the system.

初步判断是memory_target的值大于了/dev/shm的值：

[oracle@db11g ~]$ df -h /dev/shm
Filesystem Size Used Avail Use% Mounted on
tmpfs 1.9G 0 1.9G 0% /dev/shm

[oracle@db11g /]$ cat $ORACLE_HOME/dbs/spfile$ORACLE_SID.ora
…
db11g.__java_pool_size=16777216
db11g.__large_pool_size=16777216
db11g.__oracle_base=’/u01/app/oracle’#ORACLE_BASE set from environment
db11g.__pga_aggregate_target=872415232
db11g.__sga_target=1275068416
db11g.__shared_io_pool_size=0
db11g.__shared_pool_size=369098752
db11g.__streams_pool_size=0
*.audit_file_dest=’/u01/app/oracle/admin/db11g/adump’
*.audit_trail=’db’
*.compatible=’11.2.0′
*.control_files=’/dev/raw/raw5′,’/dev/raw/raw6′,’/dev/raw/raw7′CC”Z
*.db_block_size=8192
*.db_domain=”
*.db_name=’db11g’
*.db_recovery_file_dest=’/u01/app/oracle/flash_recovery_area’
*.db_recovery_file_dest_size=2G
*.diagnostic_dest=’/u01/app/oracle’
*.dispatchers=’(PROTOCOL=TCP) (SERVICE=ORCLXDB)’
*.instance_name=’db11g’
*.memory_target=2G
*.open_cursors=300
*.processes=150
*.remote_login_passwordfile=’EXCLUSIVE’
*.undo_tablespace=’UNDOTBS1′

通过比对发现：memory_target为2g，而/dev/shm总大小为1.9g，原因找到了，为什么会出现这种情况呢？

结合这两天对操作系统的修改，为了解决 Memory for crash kernel (0×0 to 0×0) notwithin permissible range，而启用了Kdump，修改了启动参数，增加了crashkernel=128M@16M，由于物理内存总大小为4g，内核划走了128m的内存，总可用物理内存就没有4g了，而/dev/shm的默认大小为物理内存的一半。因此要修改参数配置文

件/etc/fstab，将/dev/shm设为固定2g即可,然后重新挂载，启动数据库。操作如下：

[root@db11g ~]# cat /etc/fstab
LABEL=/                 /                       ext3    defaults        1 1
/dev/sdb1               /u01                    ext3    defaults        1 1
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
LABEL=SWAP-sda5         swap                    swap    defaults        0 0
LABEL=SWAP-sda6         swap                    swap    defaults        0 0
[root@db11g ~]# vi /etc/fstab

LABEL=/                 /                       ext3    defaults        1 1
/dev/sdb1               /u01                    ext3    defaults        1 1
tmpfs                   /dev/shm                tmpfs   defaults,size=2g        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
LABEL=SWAP-sda5         swap                    swap    defaults        0 0
LABEL=SWAP-sda6         swap                    swap    defaults        0 0

[root@db11g ~]# mount -o remount /dev/shm
[root@db11g ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              57G  3.1G   51G   6% /
/dev/sdb1             9.4G  5.9G  3.2G  66% /u01
tmpfs                 2.0G     0  2.0G   0% /dev/shm
[root@db11g ~]# su - oracle
[oracle@db11g ~]$ sqlplus "/as sysdba"

SQL*Plus: Release 11.2.0.1.0 Production on Mon Jul 11 13:04:49 2011

Copyright (c) 1982, 2009, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup
ORACLE instance started.

Total System Global Area 2042241024 bytes
Fixed Size                  1337548 bytes
Variable Size            1174406964 bytes
Database Buffers          855638016 bytes
Redo Buffers               10858496 bytes
Database mounted.
Database opened.
SQL>
通过固定/dev/shm大小，解决了ORACLE 11G ORA-00845: MEMORY_TARGET not supported on this system错误。