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 removed
ORA-27300: OS system dependent operation:semop failed with status: 43
ORA-27301: OS failure message: Identifier removed
ORA-27302: failure occurred at: sskgpwwait1
Fri Sep 09 16:50:53 2016
Errors in file /d12/app/oracle/diag/rdbms/rac12c/rac12c2/trace/rac12c2_rmv0_20798.trc:
ORA-27157: OS post/wait facility removed
Fri Sep 09 16:50:53 2016
Errors in file /d12/app/oracle/diag/rdbms/rac12c/rac12c2/trace/rac12c2_q005_21328.trc:
ORA-27157: OS post/wait facility removed
ORA-27300: OS system dependent operation:semop failed with status: 43
ORA-27301: OS failure message: Identifier removed
ORA-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 removed
ORA-27300: OS system dependent operation:semop failed with status: 43
ORA-27301: OS failure message: Identifier removed
ORA-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 kgxgncin
KFOD-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 instance
 
2015/11/20 21:38:45 CLSRSC-184: Configuration of ASM failed
2015/11/20 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 error
ip: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)