当检查oracle实例后台进程不存在这时启动启动数据库报错:

ORA-01081: "cannot start already-running ORACLE - shut it down first"

造成此种原因是

Orphaned shared memory segments and semaphores did not get cleared properly

from the last instance shutdown.

在oracle实例最后一次shutdown时，某一个孤立的共享内存段和信号没有被清理干净

解决方法

可以利用ipcs来找出共享内存段或者信号，利用ipcrm来手动清除

orphaned shared memory segments（孤立的共享内存段） 和semaphores（信号量）

[root@wl ~]# ipcs -a

------ Shared Memory Segments --------

keyshmid owner perms bytes nattchstatus

0x00000000 688138oracle6404096 0

0x00000000 720907oracle6404096 0

------ Semaphore Arrays --------

keysemid owner perms nsems

0x000000a7 0 root 6001

0x00000000 688138oracle6404096 0

0x00000000 720907oracle6404096 0

[root@wl ~]# ipcs -m

------ Shared Memory Segments --------

keyshmid owner perms bytes nattchstatus

0x00000000 688138oracle6404096 0

0x00000000 720907oracle6404096 0

[root@wl ~]# ipcrm - m 720907

ipcs： 检查分配的共享内存

ipcrm：手动释放共享内存段

取得ipc信息：

ipcs [-m|-q|-s]

-m 输出有关共享内存(shared memory)的信息

-q 输出有关信息队列(message queue)的信息

-s 输出有关“信号量”(semaphore)的信息

-a 使用所有打印选项. (针对 -b, -c, -o, -p, and -t的速记符)

Example:

ipcrm -mshmid 号 - for shared memory

ipcrm -ssemid 号 - for semaphores

OR

Shutdown all the instances belonging to the user. Next, run "ipcs -b" to find the remaining IPC

facilities, owned by the same user, and remove them. However, if you're running multiple production

instances, this may not be acceptable.

在多实例的情况下

1. 运行

ipcs -a > /tmp/ipcs_before.out

2. 用 SQL*Plus 连接所有实例做一个简单的查询

select * from dual;

3. 再次运行

ipcs -a > /tmp/ipcs_after.out

4. 对比 "/tmp/ipcs_before.out" 与 "/tmp/ipcs_after.out" 文件

查找 LPID 没有改变的共享内存段

These are the orphaned shared memory segments you are looking for:

LPID 显示最后过程中附加或者分立共享内存段的进程 ID

因为，通过在每一个活着的实例中执行查询，你会涉及到属于各自实例的共享内存段，

但是未涉及的共享内存段将变成孤立的一个

5. After identifying the orphaned shared memory segments, you can find

the orphaned semaphores by locating the semaphores with the same

value of CTIME in "ipcs -a" output as the value of CTIME for the

orphaned shared memory segments: CTIME shows the time when the

associated entry was created or changed.

在识别孤立的共享内存段后，可以通过ipcs -a的输出确定具有相同CTIME值的信号找到孤立的共享内存段

作为相关孤立共享内存段的值