运维班里一学生做实验，启动ASM实例，结果报错如下：
SQL> startup
ORA-27154: post/wait create failed
ORA-27300: OS system dependentoperation:semget failed with status: 28
ORA-27301: OS failure message: No spaceleft on device
ORA-27302: failure occurred at:sskgpsemsper
OS：Redhat 5.6
OS：11.2.0.1
--查看磁盘信息：
[root@lab01 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 27G 11G 15G 43% /
tmpfs 506M 0 506M 0% /dev/shm
该问题存在与11.2.0.1 之后的版本，导致的原因是因为semmns 的值太低。 该值在/etc/sysctl.conf中配置。
格式如下：
sem = semmsl semmns semopm semmni
kernel.sem = 256 32768 100 228
semaphores 参数的优化原则如下：
1. Calculate the minimum total semaphorerequirements using the following formula:
2*sum (process parameters of all databaseinstances on the system) + overhead for background processes + system and otherapplications.
2. Set semmns (total semaphores systemwide)to this total.
3. Set semmsl (semaphores for each set ) to256
4. Set semmni (total semaphores sets) tosemmns devided by semmsl, rounded up to the nearest multiple of 1024
因此该问题的解决方法就是在/etc/sysctl.conf文件中替换kernel.sem为如下值：
kernel.sem = 256 32768 100 228
--顺便查了一下我自己的测试环境，这个是Oracle preinstall设置的值：
[oracle@dave ~]$ cat /etc/sysctl.conf|grepsem
# oracle-rdbms-server-11gR2-preinstallsetting for kernel.sem is '250 32000 100 128'
kernel.sem = 250 32000 100 128
修改之后，成功启动：
[grid@lab01 dbs]$ sqlplus / as sysasm
SQL*Plus: Release 11.2.0.1.0 Production onTue Dec 3 06:53:50 2013
Copyright (c) 1982, 2009, Oracle. All rights reserved.
Connected to an idle instance.
SQL> startup
ASM instance started
Total System Global Area 284565504 bytes
Fixed Size 1336036 bytes
Variable Size 258063644 bytes
ASM Cache 25165824 bytes
ASM diskgroups mounted
===========================================================
SQL> select * from v$version;
BANNER
--------------------------------------------------------------------------------
Oracle Database 11g Enterprise EditionRelease 11.2.0.1.0 - Production
PL/SQL Release 11.2.0.1.0 - Production
CORE 11.2.0.1.0 Production
TNS for Linux: Version 11.2.0.1.0 -Production
NLSRTL Version 11.2.0.1.0 - Production
------------------------------------------------------------
[grid@lab01 ~]$ crs_stat -t
Name Type Target State Host
------------------------------------------------------------
ora.DATA.dg ora....up.type ONLINE ONLINE lab01
ora.FRA.dg ora....up.type ONLINE ONLINE lab01
ora....ER.lsnr ora....er.type ONLINE ONLINE lab01
ora.asm ora.asm.type ONLINE ONLINE lab01
ora.cssd ora.cssd.type ONLINE ONLINE lab01
ora.diskmon ora....on.type ONLINE ONLINE lab01
ora.lab01.db ora....se.type ONLINE ONLINE lab01
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