想启动Oracle的OEM服务，运行emctl start dbconsole，结果出现如下报错信息：
/u01/app/oracle/product/11.2.0/dbhome_1/oc4j/j2ee/OC4J_DBConsole_wjq.comsys.com_OraDB11g
not found。要想打开OEM的web管理程序，必须先启动Database listener，再启动Datebase Control端口监控程序，但是碰到下面的问题：
[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.
其实产生的这样的情况，可能是em资料库配置不正确或者是dbcotrol没有配置好。
解决方法：
①重建em资料
[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 >
然后直接进入http://wjq.comsys.com:5500/em/,输入账户sys和密码******，选择sysdba权限，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个产品，database control和grid control。Grid control需要下载单独的光盘安装。在用DBCA建库的时候，可以选择是否启用dbcontrol，启用的话需要在数据库中建立一个sysman的 schema，用于保存EM的一些数据，这个就是EM的资料库(repository)。使用命令行工具emca可以创建，修改，重建或者删除 dbcontrol的配置。
emca
-repos create: 创建新的 Database Control 资料档案库
emca -repos drop: 删除当前的 Database Control 资料档案库
emca -repos recreate: 删除当前的 Database Control 资料档案库并重新创建一个
emca -config dbcontrol db：配置数据库的 Database Control
emca -deconfig dbcontrol db：取消数据库的 Database Control
特别注意：
（1）如果服务器上存在多个数据库，必须在启动Database control之前设置ORACLE_SID环境变量
（2）最好使用静态IP地址来配置服务器
常用的命令语法：
emca -repos create创建一个EM资料库
emca -repos recreate重建一个EM资料库
emca -repos drop删除一个EM资料库
emca -config dbcontrol db配置数据库的 Database Control
emca -deconfig dbcontrol db删除数据库的 Database Control配置
emca -reconfig ports 重新配置db control和agent的端口
emctl start console启动EM console服务，使用前需要先设置ORACLE_SID环境变量
emctl stop console停止EM console服务，使用前需要先设置ORACLE_SID环境变量
注：通过查看$ORACLE_HOME/install/portlist.ini 文件可以知道当前dbcontrol正在使用的端口，默认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可以启动/停止console服务，察看服务状态等。
作者：SEian.G（苦练七十二变，笑对八十一难）
