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12C RAC中的一个数据库实例自动crash并报ORA-27157、ORA-27300等错误
rhel7.2上安装12C RAC数据库后，其中一个数据库实例经常会自动crash。查看alert日志发现以下错误信息：
Errors in file /d12/app/oracle/diag/rdbms/rac12c/rac12c2/trace/rac12c2_j000_21047.trc:ORA-27157: OS post/wait facility removedORA-27300: OS system dependent operation:semop failed with status: 43ORA-27301: OS failure message: Identifier removedORA-27302: failure occurred at: sskgpwwait1Fri Sep 09 16:50:53 2016Errors in file /d12/app/oracle/diag/rdbms/rac12c/rac12c2/trace/rac12c2_rmv0_20798.trc:ORA-27157: OS post/wait facility removedFri Sep 09 16:50:53 2016Errors in file /d12/app/oracle/diag/rdbms/rac12c/rac12c2/trace/rac12c2_q005_21328.trc:ORA-27157: OS post/wait facility removedORA-27300: OS system dependent operation:semop failed with status: 43ORA-27301: OS failure message: Identifier removedORA-27302: failure occurred at: sskgpwwait1
错误原因描述：
在rhel7.2中，systemd-logind服务引入了一个新特性：在一个user完全退出OS后会remove掉所有的IPC对象。
该特性由/etc/systemd/logind.conf参数文件中RemoveIPC选项来控制。详细请看man logind.conf(5)。
在rhel7.2中，RemoveIPC的默认值是yes
因此，当最后一个oracle或者grid用户退出时，操作系统会remove掉这个user的shared memory segments和semaphores
而Oracle ASM和database的SGA需要使用 shared memory segments，因此remove shared memory segments将会crash掉Oracle ASM和database instances。
请参考Redhat bug 1264533 - https://bugzilla.redhat.com/show_bug.cgi?id=1264533
这个问题会影响使用shared memory segments和semaphores的所有应用，因此，Oracle ASM 实例和Oracle Database 实例均受到影响。
oel7.2为了避免这个问题，在/etc/systemd/logind.conf配置文件中明确设置RemoveIPC为no。
该问题会导致的现象：
1) Installing 11.2 and 12c GI/CRS fails, because ASM crashes towards the end of the installation.2) Upgrading to 11.2 and 12c GI/CRS fails.3) After Redhat Linux is upgraded to 7.2, 11.2 and 12c ASM and database instances crash.
systemd-logind可能会在任何时候remove IPC对象，发生错误的时候对应的日志现象也不同。比如：
Most common error that occurs is that the following is found in the asm or database alert.log:ORA-27157: OS post/wait facility removedORA-27300: OS system dependent operation:semop failed with status: 43ORA-27301: OS failure message: Identifier removedORA-27302: failure occurred at: sskgpwwait1
The second observed error occurs during installation and upgrade when asmca fails with the following error:KFOD-00313: No ASM instances available. CSS group services were successfully initilized by kgxgncinKFOD-00105: Could not open pfile ‘init@.ora‘
The third observed error occurred during installation and upgrade:Creation of ASM password file failed. Following error occurred: Error in Process: /d12/app/12.1.0/grid/bin/orapwd Enter password for SYS:OPW-00009: Could not establish connection to Automatic Storage Management instance2015/11/20 21:38:45 CLSRSC-184: Configuration of ASM failed2015/11/20 21:38:46 CLSRSC-258: Failed to configure and start ASM
The fourth observed error is the following message is found in the /var/log/messages file around the time that asm or database instance crashed:Nov 20 21:38:43 testc201 kernel: traps: oracle[24861] trap divide errorip:3896db8 sp:7ffef1de3c40 error:0 in oracle[400000+ef57000]
修改方法：
1).设置/etc/systemd/logind.conf中RemoveIPC=no
2).重启服务器或者重启systemd-logind
重启systemd-logind：
# systemctl daemon-reload# systemctl restart systemd-logind
MOS Doc:
ALERT: Setting RemoveIPC=yes on Redhat 7.2 Crashes ASM and Database Instances as Well as Any Application That Uses a Shared Memory Segment (SHM) or Semaphores (SEM) (Doc ID 2081410.1)
12C RAC中的一个数据库实例自动crash并报ORA-27157、ORA-27300等错误