我的一个客户的Oracle数据库不能启动，出现下面的提示：
ORA-27154: post/wait create failed
ORA-27300: OS system dependent operation:semget failed with status: 28
ORA-27301: OS failure message: No space left on device
ORA-27302: failure occurred at: sskgpcreates
乍一看以为是硬盘空间不够，使用du进行检查，发现空间没有问题。而且这个错误是在实例启动到nomount状态时出现的，这个过程中只需要访问数据库的参数文件，并不涉及到硬盘空间的问题。在rman中启动dummy实例（export ORACLE_SID=dummy）试试，也出现了同样的错误，见下图：
$ export ORACLE_SID=dummy
$ rman target /
Recovery Manager: Release 19.0.0.0.0 - Production on Tue Jan 9 10:14:24 2024
Version 19.3.0.0.0Copyright (c) 1982, 2019, Oracle and/or its affiliates. All rights reserved.connected to target database: DUMMY (not mounted)
RMAN> startup nomount;
startup failed:0RA-01078:failure inprocessing systemparameters
LRM-00109:could notopen parameter file'/u01/app/oracle/product/19.3.0/db/dbs/initdummy.ora
starting Oracleinstance without parameter file forretrieval of spfile
RMAN-00571:===================================================================
RMAN-00569:============ERROR MESSAGE STACK FOLLOWS============================
RMAN-00571:===================================================================
RMAN-03002:fatlure of startup command at 01/03/2024 14:48:06
RMAN-04014:startup failed: 0RA-27154: post/wait create failed
ORA-27300:OS system dependent operation:semget failed with status:28
ORA-27301:Os failuremessage:No spaceleft on device
oRA-27302:failure 0ccurred at:sskgpcreates
RMAN>
通过检查pmon进程查看已经启动的实例，发现有5个已经启动的实例。到metalink上面找一下，发现一个相似的文档，Doc ID 314179.1。从文档中的分析，可能是Linux的信号量不足造成的，把信号量增大一倍，重启启动dummy实例，成功了！相关操作见下图：
