Applies to:
Oracle Server - Enterprise Edition - Version: 8.1.7.4 to 11.2.0.2.0 - Release: 8.1.7 to 11.2
Generic UNIX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@rac01 ~]# ipcs -a ------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status      0x4e44b264 557069     oracle    640        287309824  25
0xd06e774c 524302     oracle    640        132120576  16                      ------ Semaphore Arrays --------
key        semid      owner      perms      nsems
0x000000a7 0          root      600        1
0x2e7fd0cc 131073     oracle    640        44
0x334b5294 262146     oracle    640        154    [root@rac01 ~]# ipcs -m ------ Shared Memory Segments --------
key        shmid      owner      perms      bytes      nattch     status      0x4e44b264 557069     oracle    640        287309824  25
0xd06e774c 524302     oracle    640        132120576  16                      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 -m    shmid 号   - for shared memory ipcrm -s    semid  号      - for semaphores ORShutdown 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NOTE:  This step may not be necessary on the platforms implementing post-wait kernel extension (AT&T Unix, AIX), when semaphores  are not used by Oracle at all.