我们在使用Oracle时， 可以利用Oracle自带的EM(Enterprise Manager)来更方便的管理我们的数据库。但是有时候我们的em却有时候无法连接，造成这个问题的原因有好多，例如没有正确的配置hostname,或者操作系统的防火墙问题等等。如果出现了问题，我们能否快速的重建em呢？答案是肯定的。我们可以通过Oracle官方文档来参照。但是如果我们对于em里面如此多的配置命令和选项比较头大的时候，你就可以参照此文来重新创建EM。
首先需要设置好环境变量ORACLE_HOSTNAME
export ORACLE_HOSTNAME=testbox.localdomain
然后再执行：
emca -config dbcontrol db -repos recreate
如果这个方法不行的话，你可以手动先drop掉你当前的repo
emca -deconfig dbcontrol db -repos drop
然后再重新创建
emca -config dbcontrol db -repos create
此间过程比较长，大概需要十分钟左右来创建。然后你就可以看到如下提示：
[oracle@testbox j2ee]$ emca -config dbcontrol db -repos create STARTED EMCA at Jul , :: PM
EM Configuration Assistant, Version 11.2.0.3. Production
Copyright (c) , , Oracle. All rights reserved. Enter the following information:
Database SID: erin
Listener ORACLE_HOME [ /u01/app/oracle/product/11.2./db_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./db_1 Local hostname ................ testbox.localdomain
Listener ORACLE_HOME ................ /u01/app/oracle/product/11.2./db_1
Listener port number ................
Database SID ................ erin
Email address for notifications ...............
Outgoing Mail (SMTP) server for notifications ............... -----------------------------------------------------------------
Do you wish to continue? [yes(Y)/no(N)]: yes
Jul , :: PM oracle.sysman.emcp.EMConfig perform
INFO: This operation is being logged at /u01/app/oracle/cfgtoollogs/emca/erin/emca_2014_07_01_22_50_24.log.
Jul , :: PM oracle.sysman.emcp.EMReposConfig createRepository
INFO: Creating the EM repository (this may take a while) ... Jul , :: PM oracle.sysman.emcp.EMReposConfig invoke
INFO: Repository successfully created
Jul , :: PM oracle.sysman.emcp.EMReposConfig uploadConfigDataToRepository
INFO: Uploading configuration data to EM repository (this may take a while) ... Jul , :: PM oracle.sysman.emcp.EMReposConfig invoke
INFO: Uploaded configuration data successfully
Jul , :: PM oracle.sysman.emcp.util.DBControlUtil secureDBConsole
INFO: Securing Database Control (this may take a while) ...
Jul , :: PM oracle.sysman.emcp.util.DBControlUtil secureDBConsole
INFO: Database Control secured successfully.
Jul , :: PM oracle.sysman.emcp.util.DBControlUtil startOMS
INFO: Starting Database Control (this may take a while) ...
Jul , :: PM oracle.sysman.emcp.EMDBPostConfig performConfiguration
INFO: Database Control started successfully
Jul , :: PM oracle.sysman.emcp.EMDBPostConfig performConfiguration
INFO: >>>>>>>>>>> The Database Control URL is https://testbox.localdomain:5500/em <<<<<<<<<<<
Jul , :: PM oracle.sysman.emcp.EMDBPostConfig invoke
WARNING:
************************ WARNING ************************ Management Repository has been placed in secure mode wherein Enterprise Manager data will be encrypted. The encryption key has been placed in the file: /u01/app/oracle/product/11.2./db_1/testbox.localdomain_erin/sysman/config/emkey.ora. Ensure this file is backed up as the encrypted data will become unusable if this file is lost. ***********************************************************
Enterprise Manager configuration completed successfully
FINISHED EMCA at Jul , :: PM
标注的红色部分就是我们的em的访问地址。