环境：RHEL5.6 + Oracle11.2.0.3双节点RAC
故障现象：节点1实例没有启动成功，节点2正常启动。
?1.故障现象
?2.解决过程
?3.总结
1.故障现象尝试启动RAC 节点1，遭遇ORA-01105，ORA-01606：
SQL> startup mount;
ORACLE instance started.Total System Global Area 9.4869E+10 bytesFixed Size 2264056 bytesVariable Size 5.0197E+10 bytesDatabase Buffers 4.4560E+10 bytesRedo Buffers 109174784 bytesORA-01105: mount is incompatible with mounts by other instancesORA-01606: parameter not identical to that of another mounted instance数据库节点1目前状态是NOMOUNT.
2.解决过程错误代码说明：
$ oerr ora 110501105, 00000, "mount is incompatible with mounts by other instances"// *Cause: An attempt to mount the database discovered that another instance// mounted a database by the same name, but the mount is not// compatible. Additional errors are reported explaining why.// *Action: See accompanying errors.$ oerr ora 160601606, 00000, "parameter not identical to that of another mounted instance"// *Cause: A parameter was different on two instances.// *Action: Modify the initialization parameter and restart.查询gc_隐含参数
set linesize 333col name for a35col description for a66col value for a30SELECT i.ksppinm name, i.ksppdesc description, CV.ksppstvl VALUEFROM sys.x$ksppi i, sys.x$ksppcv CV WHERE i.inst_id = USERENV ('Instance') AND CV.inst_id = USERENV ('Instance') AND i.indx = CV.indx AND i.ksppinm LIKE '/_gc%' ESCAPE '/' ORDER BY REPLACE (i.ksppinm, '_', ''); 查询结果如下（部分相同值的参数已省略）：
--节点1：_gc_policy_time how often to make object policy decisions in minutes 0_gc_read_mostly_flush_check if TRUE, optimize flushes for read mostly objects FALSE_gc_read_mostly_locking if TRUE, enable read-mostly locking FALSE--节点2：_gc_policy_time how often to make object policy decisions in minutes 10_gc_read_mostly_flush_check if TRUE, optimize flushes for read mostly objects FALSE_gc_read_mostly_locking if TRUE, enable read-mostly locking TRUE发现问题，_gc_policy_time隐藏参数，_gc_read_mostly_locking隐藏参数，2个节点值不一致。
解决方法：根据现在正常运行的节点2的值，重新设置这两个值：
alter system set "_gc_read_mostly_locking"=true scope=spfile sid='*';
alter system set "_gc_policy_time"=10 scope=spfile sid='*';
或者两边节点都停下来,重起.
--正常关闭节点1：shutdown immediate;
--正常启动节点1：startup实际执行过程如下：
SQL> alter system set "_gc_read_mostly_locking"=true scope=spfile sid='*';
System altered.
SQL> alter system set "_gc_policy_time"=10 scope=spfile sid='*';
System altered.
SQL> shutdown immediate;ORA-01507: database not mountedORACLE instance shut down.
SQL> startupORACLE instance started.Total System Global Area 9.4869E+10 bytesFixed Size 2264056
bytesVariable Size 5.1271E+10 bytesDatabase Buffers 4.3487E+10 bytesRedo Buffers
109174784 bytesDatabase mounted.Database opened.
至此RAC节点1启动成功。
3.总结我这里,其实就是修改了 gc_read_mostly_locking gc_policy_time 参数,关闭了 drm导致.