想啟動Oracle的OEM服務，運行emctl start dbconsole，結果出現如下報錯信息：
       /u01/app/oracle/product/11.2.0/dbhome_1/oc4j/j2ee/OC4J_DBConsole_wjq.comsys.com_OraDB11g not found。要想打開OEM的web管理程序，必須先啟動Database listener，再啟動Datebase Control端口監控程序，但是碰到下面的問題：

[oracle@wjq ~]$ emctl start dbconsole

OC4J Configuration issue. /u01/app/oracle/product/11.2.0/dbhome_1/oc4j/j2ee/OC4J_DBConsole_wjq.comsys.com_OraDB11g not found.

其實產生的這樣的情況，可能是em資料庫配置不正確或者是dbcotrol沒有配置好。

解決方法：   

①重建em資料

[oracle@wjq ~]$ emca -repos recreate 

STARTED EMCA at Nov 3, 2017 4:35:17 PM

EM Configuration Assistant, Version 11.2.0.3.0 Production

Copyright (c) 2003, 2011, Oracle.  All rights reserved.

Enter the following information:

Database SID: seiang11g

Listener port number: 1521

Password for SYS user: 

Password for SYSMAN user: 

----------------------------------------------------------------------

WARNING : While repository is dropped the database will be put in quiesce mode.

----------------------------------------------------------------------

Do you wish to continue? [yes(Y)/no(N)]: Y

Nov 3, 2017 4:35:34 PM oracle.sysman.emcp.EMConfig perform

INFO: This operation is being logged at /u01/app/oracle/cfgtoollogs/emca/OraDB11g/emca_2017_11_03_16_35_16.log.

Nov 3, 2017 4:35:34 PM oracle.sysman.emcp.EMReposConfig invoke

INFO: Dropping the EM repository (this may take a while) ...

Nov 3, 2017 4:36:47 PM oracle.sysman.emcp.EMReposConfig invoke

INFO: Repository successfully dropped

Nov 3, 2017 4:36:47 PM oracle.sysman.emcp.EMReposConfig createRepository

INFO: Creating the EM repository (this may take a while) ...

Nov 3, 2017 4:40:32 PM oracle.sysman.emcp.EMReposConfig invoke

INFO: Repository successfully created

Enterprise Manager configuration completed successfully

FINISHED EMCA at Nov 3, 2017 4:40:32 PM

②配置dbcontrol

[oracle@wjq ~]$ emca -config dbcontrol db

STARTED EMCA at Nov 3, 2017 2:29:41 PM

EM Configuration Assistant, Version 11.2.0.3.0 Production

Copyright (c) 2003, 2011, Oracle.  All rights reserved.

Enter the following information:

Database SID: seiang11g

Listener port number: 1521

Listener ORACLE_HOME [ /u01/app/oracle/product/11.2.0/dbhome_1 ]:

Password for SYS user: 

Password for DBSNMP user: 

Password for SYSMAN user: 

Email address for notifications (optional):

Outgoing Mail (SMTP) server for notifications (optional):

-----------------------------------------------------------------

You have specified the following settings

Database ORACLE_HOME ................ /u01/app/oracle/product/11.2.0/dbhome_1

Local hostname ................ wjq.comsys.com

Listener ORACLE_HOME ................ /u01/app/oracle/product/11.2.0/dbhome_1

Listener port number ................ 1521

Database SID ................ seiang11g

Email address for notifications ...............

Outgoing Mail (SMTP) server for notifications ...............

-----------------------------------------------------------------

Do you wish to continue? [yes(Y)/no(N)]: y^H

Nov 3, 2017 2:30:36 PM oracle.sysman.emcp.EMConfig perform

INFO: This operation is being logged at /u01/app/oracle/cfgtoollogs/emca/OraDB11g/emca_2017_11_03_14_29_40.log.

Nov 3, 2017 2:30:39 PM oracle.sysman.emcp.EMReposConfig uploadConfigDataToRepository

INFO: Uploading configuration data to EM repository (this may take a while) ...

Nov 3, 2017 2:32:36 PM oracle.sysman.emcp.EMReposConfig invoke

INFO: Uploaded configuration data successfully

Nov 3, 2017 2:32:38 PM oracle.sysman.emcp.util.DBControlUtil secureDBConsole

INFO: Securing Database Control (this may take a while) ...

Nov 3, 2017 2:32:53 PM oracle.sysman.emcp.util.PlatformInterface executeCommand

WARNING: Error executing /u01/app/oracle/product/11.2.0/dbhome_1/bin/emctl secure dbconsole -host wjq.comsys.com -sid OraDB11g

Nov 3, 2017 2:32:53 PM oracle.sysman.emcp.EMDBPostConfig performConfiguration

WARNING: Error securing Database control.

Nov 3, 2017 2:32:53 PM oracle.sysman.emcp.EMDBPostConfig setWarnMsg

INFO: Error securing Database Control. Database Control has been brought-up in non-secure mode. To secure the Database Control execute the following command(s):

 1) Set the environment variable ORACLE_UNQNAME to Database unique name

 2) /u01/app/oracle/product/11.2.0/dbhome_1/bin/emctl stop dbconsole

 3) /u01/app/oracle/product/11.2.0/dbhome_1/bin/emctl config emkey -repos -sysman_pwd < Password for SYSMAN user > 

 4) /u01/app/oracle/product/11.2.0/dbhome_1/bin/emctl secure dbconsole -sysman_pwd < Password for SYSMAN user > 

 5) /u01/app/oracle/product/11.2.0/dbhome_1/bin/emctl start dbconsole

 To secure Em Key, run /u01/app/oracle/product/11.2.0/dbhome_1/bin/emctl config emkey -remove_from_repos -sysman_pwd < Password for SYSMAN user >

Nov 3, 2017 2:32:53 PM oracle.sysman.emcp.util.DBControlUtil startOMS

INFO: Starting Database Control (this may take a while) ...

Nov 3, 2017 2:32:58 PM oracle.sysman.emcp.EMDBPostConfig performConfiguration

INFO: Database Control started successfully

Nov 3, 2017 2:32:58 PM oracle.sysman.emcp.EMDBPostConfig performConfiguration

INFO: >>>>>>>>>>> The Database Control URL is http://wjq.comsys.com:5500/em <<<<<<<<<<<

Error securing Database Control. Database Control has been brought-up in non-secure mode. To secure the Database Control execute the following command(s):

 1) Set the environment variable ORACLE_UNQNAME to Database unique name

 2) /u01/app/oracle/product/11.2.0/dbhome_1/bin/emctl stop dbconsole

 3) /u01/app/oracle/product/11.2.0/dbhome_1/bin/emctl config emkey -repos -sysman_pwd < Password for SYSMAN user > 

 4) /u01/app/oracle/product/11.2.0/dbhome_1/bin/emctl secure dbconsole -sysman_pwd < Password for SYSMAN user > 

 5) /u01/app/oracle/product/11.2.0/dbhome_1/bin/emctl start dbconsole

 To secure Em Key, run /u01/app/oracle/product/11.2.0/dbhome_1/bin/emctl config emkey -remove_from_repos -sysman_pwd < Password for SYSMAN user >

然后直接進入http://wjq.comsys.com:5500/em/,輸入賬戶sys和密碼******，選擇sysdba權限，就能正常看到基于WEB的EM了。
   
   Oracle11G的EM采用了web方式，并且分成了2個產品，database control和grid control。Grid control需要下載單獨的光盤安裝。在用DBCA建庫的時候，可以選擇是否啟用dbcontrol，啟用的話需要在數據庫中建立一個sysman的 schema，用于保存EM的一些數據，這個就是EM的資料庫(repository)。使用命令行工具emca可以創建，修改，重建或者刪除 dbcontrol的配置。

emca -repos create: 創建新的 Database Control 資料檔案庫
emca -repos drop: 刪除當前的 Database Control 資料檔案庫
emca -repos recreate: 刪除當前的 Database Control 資料檔案庫并重新創建一個
emca -config dbcontrol db：配置數據庫的 Database Control

emca -deconfig dbcontrol db：取消數據庫的 Database Control

特別注意：

（1）如果服務器上存在多個數據庫，必須在啟動Database control之前設置ORACLE_SID環境變量
（2）最好使用靜態IP地址來配置服務器

常用的命令語法：

emca -repos create創建一個EM資料庫

emca -repos recreate重建一個EM資料庫

emca -repos drop刪除一個EM資料庫

emca -config dbcontrol db配置數據庫的 Database Control

emca -deconfig dbcontrol db刪除數據庫的 Database Control配置

emca -reconfig ports 重新配置db control和agent的端口

emctl start console啟動EM console服務，使用前需要先設置ORACLE_SID環境變量

emctl stop console停止EM console服務，使用前需要先設置ORACLE_SID環境變量

注：通過查看$ORACLE_HOME/install/portlist.ini 文件可以知道當前dbcontrol正在使用的端口，默認dbcontrol http端口1158，agent端口3938。如果要重新配置端口，可以使用如下命令：

emca -reconfig ports -dbcontrol_http_port 1159

emca -reconfig ports -agent_port 3939

使用命令行工具emctl可以啟動/停止console服務，察看服務狀態等。

作者：SEian.G（苦練七十二變，笑對八十一難）