We can also recreate the dbcontrol manually .I am providing the steps below:

Please do the following steps to recreate the database control which will allow new connections to database:Make sure that the database and the listener is up and running.

1. Logon SQLPLUS as user SYS and drop the sysman account and mangement objects:

a. drop user sysman cascade;

b. drop role MGMT_USER;

c. drop user MGMT_VIEW cascade;

d. drop public synonym MGMT_TARGET_BLACKOUTS;

e. drop public synonym SETEMVIEWUSERCONTEXT;

2. Manually remove the following folders from BOTH nodes of cluster:

/u01/app/oracle/product/10.2.0/db_1/oraclerac1_orcl1

/u01/app/oracle/product/10.2.0/db_1/oraclerac1_orcl2

/u01/app/oracle/product/10.2.0/db_1\oc4j\j2ee\OC4J_DBConsole_oraclerac1_orcl1

/u01/app/oracle/product/10.2.0/db_1\oc4j\j2ee\OC4J_DBConsole_oraclerac1_orcl2

/u01/app/oracle/product/10.2.0/db_1/cfgtoollogs/emca/orclcinfa/*

NOTE: Please ensure that the above steps are done from all nodes of cluster.

3.Set the ORACLE_HOME and ORACLE_SID

From ORACLE_HOME/bin

emca -config dbcontrol db -repos create -cluster

and give the necessary parameters.

At the end you will get an URL which can be used to access the DBConsole.

Reconfiguring the dbconsole means recreating the repository of dbconsole.

Impact: We will loose the Historical information of metrics collected by dbconsole earlier

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1.1 建立EM资料库

emca -repos drop    删除一个EM资料库

emca -repos create 创建一个EM资料库

emca -repos recreate重建一个EM资料库

1.2 配置dbcontrol    

emca -deconfig dbcontrol db    删除数据库的 Database Control配置

emca -config dbcontrol db       配置数据库的 Database Control