Oracle11g RAC + DG 搭建过程中，在备库进行duplicate时报错如下：

[oracle@xxxx-dg:/u01/app/oracle/11.2/db_1/dbs]$rmantargetsys/password@racdbauxiliarysys/password@racdgnocatalogRecoveryManager:Release11.2.0.4.0-ProductiononFriAbc2117:33:01xxxxCopyright(c)1982,2011,Oracleand/oritsaffiliates.Allrightsreserved.connectedtotargetdatabase:RACDB(DBID=938466123)usingtargetdatabasecontrolfileinsteadofrecoverycatalogconnectedtoauxiliarydatabase(notstarted)RMAN>duplicatetargetdatabaseforstandbyfromactivedatabasenofilenamecheck;StartingDuplicateDbatxxxx-xx-2117:33:04RMAN-00571:===========================================================RMAN-00569:===============ERRORMESSAGESTACKFOLLOWS===============RMAN-00571:===========================================================RMAN-03002:failureofDuplicateDbcommandatxx/21/xxxx17:33:05RMAN-05501:abortingduplicationoftargetdatabaseRMAN-06403:couldnotobtainafullyauthorizedsessionRMAN-04006:errorfromauxiliarydatabase:ORA-01034:ORACLEnotavailableORA-27101:sharedmemoryrealmdoesnotexistLinux-x86_64Error:2:NosuchfileordirectoryRMAN>exit

通过

RMAN-04006:errorfromauxiliarydatabase:ORA-01034:ORACLEnotavailable

ORA-27101:sharedmemoryrealmdoesnotexistLinux-x86_64Error:2:Nosuchfileordirectory

可看到，由于连接数据库失败导致的，回头发现，之前通过Rman连接数据库时，备库已经是启动到nomount状态了，但是当进行

RMAN>duplicatetargetdatabaseforstandbyfromactivedatabasenofilenamecheck;

时，备库不知由于什么原因down掉了，查看alert日志，发现确实在RMAN连接上之后，备库nomount启动之后，数据库进行过shutdown immediate操作，重新将数据库启动至nomount状态，startup nomount。再次进行

duplicate

未报同样错误