ORA-00845 MEMORY_TARGET not supported on this system

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ORA-00845: MEMORY_TARGET not supported on this system

我建立虚拟机的时候选择的是8G的内存，但是检查的时候报错，我只有4G提示 Swap分区不够，

其实是可以使用DD命令解决的。

GG 同步不起。

解决Linux上11g的ORA-00845错误

下午想把一个11.2.0.2实例的memory_target AMM内存初始化参数修改到2000M，改好后重启发现实例起不来了，出现了ORA-00845错误:

[oracle@rh2 ~]$ [oracle@rh2 ~]$ sqlplus  / as sysdbaSQL*Plus: Release 11.2.0.2.0 Production on Tue May 3 19:43:50 2011Copyright (c) 1982, 2010, Oracle.  All rights reserved.Connected to an idle instance.SQL> startup nomount;ORA-00845: MEMORY_TARGET not supported on this system======================= ALERT.LOG======================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 2097152000 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 1871466496 and used is 200790016 bytes. Ensure that the mount point is /dev/shm for this directory.memory_target needs larger /dev/shm

看起来是因为采用了Automatic Memory Management的特性，所以Oracle采用了一种基于POSIX的共享内存使用风格，在AMM中Oracle不像之前版本那样利用”一整块”内存作为SGA，而是使用一块块小的”chunk”，以满足SGA与PGA之前交换内存的目的

针对上述ORA-00845错误，我们需要修改映射内存文件夹/dev/shm的装载参数，针对正在运行的Linux操作系统，可以remount这个tmpfs装载点，如:

[root@rh2 ~]# umount /dev/shmumount: /dev/shm: device is busyumount: /dev/shm: device is busy[root@rh2 ~]# ls /dev/shmJOXSHM_EXT_0_PROD1_8323079   JOXSHM_EXT_25_PROD1_8323079  ora_+ASM1_7569414_11  JOXSHM_EXT_10_PROD1_8323079  JOXSHM_EXT_26_PROD1_8323079  ora_+ASM1_7569414_12  ............/* 可以看到如果ASM实例也使用AMM的话同样会在/dev/shm目录下产生内存映像     为了umount该装载点，我们不得不首先shutdown ASM instance ! */[root@rh2 ~]# su - grid[grid@rh2 ~]$ sqlplus  / as sysdbaSQL*Plus: Release 11.2.0.2.0 Production on Tue May 3 20:05:24 2011Copyright (c) 1982, 2010, Oracle.  All rights reserved.Connected to:Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit ProductionWith the Real Application Clusters and Automatic Storage Management optionsSQL> shutdown immediate;ORA-01031: insufficient privilegesSQL> exitDisconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit ProductionWith the Real Application Clusters and Automatic Storage Management options[grid@rh2 ~]$ sqlplus  / as sysasmSQL*Plus: Release 11.2.0.2.0 Production on Tue May 3 20:05:32 2011Copyright (c) 1982, 2010, Oracle.  All rights reserved.Connected to:Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit ProductionWith the Real Application Clusters and Automatic Storage Management optionsSQL> shutdown immediate;ORA-15097: cannot SHUTDOWN ASM instance with connected client (process 1576)SQL> shutdown abort;ASM instance shutdownSQL> exitDisconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.2.0 - 64bit ProductionWith the Real Application Clusters and Automatic Storage Management options[root@rh2 ~]# umount /dev/shm[root@rh2 ~]# mount -t tmpfs shmfs -o size=4000m /dev/shm/* 这里的size指定了shm目录的装载大小，4000m可能对你的系统仍然不够，    那么你有理由设一个更大的值  */[root@rh2 ~]# mount|grep shmfsshmfs on /dev/shm type tmpfs (rw,size=4000m)Startup ASM...........[root@rh2 ~]# su - oracle[oracle@rh2 ~]$ sqlplus  / as sysdbaSQL*Plus: Release 11.2.0.2.0 Production on Tue May 3 20:09:40 2011Copyright (c) 1982, 2010, Oracle.  All rights reserved.Connected to an idle instance.SQL> startup nomount;ORACLE instance started.Total System Global Area 2087780352 bytesFixed Size                  2228072 bytesVariable Size            1476395160 bytesDatabase Buffers          603979776 bytesRedo Buffers                5177344 bytes/* 实例启动成功！ */

上述umount/mount的方式只在操作系统的此次生命周期中生效，如果重启的话shmfs目录仍会以默认方式装载；如果需要永久生效的话，我们需要修改系统参数文件/etc/fstab中的shm条目:

/* 修改前的shm装载参数 */[root@rh2 ~]# grep shm /etc/fstab tmpfs                   /dev/shm                tmpfs   defaults        0 0/* 修改后的shm装载参数 */[root@rh2 ~]# grep shm /etc/fstab tmpfs                   /dev/shm                tmpfs   rw,size=4000m   0 0

参考：

oracle启动报错：ORA-00845: MEMORY_TARGET not supported on this system

今天启动oracle的时候，报错

[root@localhost ~]#su - oracle

[oracle@localhost ~]$lsnrctl start

lsnrctl: error while loading shared libraries: /u01/app/oracle/product/11.2.0/db_1/lib/libclntsh.so.11.1: cannot restore segment prot after reloc: Permission denied

解决办法：在root用户下执行以下命令

[root@localhost ~]# setenforce 0

[root@localhost ~]#su - oracle

[oracle@localhost ~]$lsnrctl start

LSNRCTL for Linux: Version 11.2.0.1.0 - Production on 20-SEP-2012 19:03:03

Starting /u01/app/oracle/product/11.2.0/db_1/bin/tnslsnr: please wait...

TNSLSNR for Linux: Version 11.2.0.1.0 - Production
Log messages written to /u01/app/oracle/diag/tnslsnr/localhost/listener/alert/log.xml
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=localhost.localdomain)(PORT=1521)))

Connecting to (ADDRESS=(PROTOCOL=tcp)(HOST=)(PORT=1521))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 11.2.0.1.0 - Production
Start Date 20-SEP-2012 19:03:04
Uptime 0 days 0 hr. 0 min. 1 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Listener Log File /u01/app/oracle/diag/tnslsnr/localhost/listener/alert/log.xml
Listening Endpoints Summary...
(DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=localhost.localdomain)(PORT=1521)))
The listener supports no services
The command completed successfully

问题解决。

[oracle@localhost ~]$ sqlplus / as sysdba

SQL> startup

报错：ORA-00845: MEMORY_TARGET not supported on this system

问题定位：安装数据库时或者修改了参数MEMORY_TARGET或者SGA_TARGET的大小。
SGA参数的大小超过了操作系统/dev/shm的大小。
linux安装完后默认/dev/shm为物理内存的一半。

技术背景：linux大内存支持（Very Large Memory）中，使用了shmfs/tmpfs选项，ramfs也可以。
/dev/shm目录挂载类型为tmpfs，此共享内存用于交换，尤其对于大文件优势明显。
相对于ramfs，tmpfs的优势在于动态调整物理内存的占用，而ramfs不能调整。
/dev/shm与swap的区别：shm基于内存的文件系统，swap基于硬盘的文件系统。

解决方法：

1、调整MEMORY_TARGET（11G）或者SGA_TARGET（9i，10G）大小（不建议）。

2、调整/dev/shm的大小。
修改/etc/fstab，重新mount /dev/shm，然后就可以启动数据库了。

（1）查看/dev/shm 大小
df -k /dev/shm
Filesystem 1K-blocks Used Available Use% Mounted on
tmpfs 4089416 0 4089416 0% /dev/shm
（2）调整/dev/shm大小
vi /etc/fstab
#tmpfs /dev/shm tmpfs defaults 0 0
tmpfs /dev/shm tmpfs defaults,size=10240M 0 0
（3）重新加载
umount /dev/shm
mount /dev/shm
df -k /dev/shm
（4）登陆测试
sqlplus / as sysdba

至此问题得到解决。

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