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12c安装集群的时候会创建一个mgmtdb实例，这个实例是一个单实例，只能运行在一个节点上。我在之前实验的时候把该实例的内存调到了400m（为节约系统资源），由于内存过低，该实例在集群启动的时候就不会自动启动。在节点1实验打psu的时候，报错了，日志如下：
Oracle Clusterware active version on the cluster is [12.2.0.1.0]. The cluster upgrade state is [ROLLING PATCH]. The cluster active patch level is [0].
PRCR-1013 : Failed to start resource ora.mgmtdb
PRCR-1064 : Failed to start resource ora.mgmtdb on node rac01
CRS-5017: The resource action "ora.mgmtdb start" encountered the following error:
ORA-01078: failure in processing system parameters
. For details refer to "(:CLSN00107:)" in "/u01/app/grid/base/diag/crs/rac01/crs/trace/crsd_oraagent_grid.trc".
CRS-2674: Start of 'ora.mgmtdb' on 'rac01' failed
2017/08/01 16:03:35 CLSRSC-180: An error occurred while executing the command '/u01/app/grid/product/12.2.0/grid/bin/srvctl start mgmtdb -n rac01'
2017/08/01 16:03:35 CLSRSC-490: Starting the Grid Infrastructure Management Repository database failed.
After fixing the cause of failure Run opatchauto resume with session id "RWMS"
此时在grid和oracle用户下执行./opatch lsinv命令，psu是应用上了的，但是该节点的集群停止，且手工启动失败，查看alert日志，会看到如下类型的错误：
CRS-4123: Starting Oracle High Availability Services-managed resources
CLSU-00105: operating system interface has reported an internal failure
CLSU-00103: error location: canexec2
CLSU-00104: additional error information: no exe permission, file [/u01/app/grid/product/12.2.0/grid/bin/ohasd
CRS-4000: Command Start failed, or completed with errors.
2017/08/01 16:23:00 CLSRSC-117: Failed to start Oracle Clusterware stack
检查grid用户的$ORACLE_HOME/bin目录，集群启动需要的相关脚本权限变了，以octssd脚本为例，正常的owner应该为root
节点1：
[root@rac01 ~]# ll /u01/app/grid/product/12.2.0/grid/bin/octssd
-rwxr----- 1 grid oinstall 11424 Aug 1 15:57 /u01/app/grid/product/12.2.0/grid/bin/octssd
节点2：
[grid@rac02 ~]$ ll /u01/app/grid/product/12.2.0/grid/bin/octssd
-rwxr----- 1 root oinstall 11424 Jun 29 13:00 /u01/app/grid/product/12.2.0/grid/bin/octssd
这种情况下需要给这些脚本重新指定owner，此时集群能够正常启动。启动mgmtdb实例，重新应用psu还是会提示一样的错误。
此时只能回退PSU后再重新应用，回退PSU的过程中保证数据库无活动会话。
root用户下执行回退命令：$GRID_HOME//OPatch/opatchautorollback 26133434/
来源：oschina
链接：https://my.oschina.net/u/3761438/blog/1921609