An earlier blog post, Oracle 10g: Setting up The Oracle Enterprise Manager Console, has the detailed instructions for setting up the Oracle 10g OEM console. However if the database along with the RDBMS server was moved (copied over) to a different host, Oracle Enterprise Manager (OEM) refuses to start. In such cases, the error message will be similar to the following.

% emctl start dbconsole
OC4J Configuration issue. /export/pspp/oracle/oc4j/j2ee/OC4J_DBConsole_localhost_test not found.

One simple solution (there might be many) to fix this issue is to re-create the repository for the OEM console. The steps are as follows.

1. Make sure the database instance and the listener are up.
   
   
2. Unlock sysman and sys user accounts if not unlocked already.
   
   eg.,
   

   % sqlplus / as sysdba
   
   SQL*Plus: Release 10.2.0.3.0 - Production on Thu Aug 27 23:42:24 2008
   Copyright (c) 1982, 2006, Oracle.  All Rights Reserved.
   
   Connected to:
   Oracle Database 10g Enterprise Edition Release 10.2.0.3.0 - 64bit Production
   With the Partitioning, OLAP and Data Mining options
   
   SQL> alter user sysman identified by manager account unlock;
   
   User altered.
   
   SQL>  alter user sys identified by manager account unlock;
   
   User altered.
   
   SQL> quit

   
   
3. Re-create the repository.
   
   eg.,
   

   % emca -config dbcontrol db -repos recreate
   
   STARTED EMCA at Aug 27, 2008 11:43:09 PM
   EM Configuration Assistant, Version 10.2.0.1.0 Production
   Copyright (c) 2003, 2005, Oracle.  All rights reserved.
   
   Enter the following information:
   Database SID: test
   Listener port number: 1521
   Password for SYS user: manager
   Password for DBSNMP user: dbsnmp
   Password for SYSMAN user: manager
   Email address for notifications (optional):
   Outgoing Mail (SMTP) server for notifications (optional):
   -----------------------------------------------------------------
   
   You have specified the following settings
   
   Database ORACLE_HOME ................ /export/pspp/oracle
   
   Database hostname ................ matrix
   Listener port number ................ 1521
   Database SID ................ test
   Email address for notifications ...............
   Outgoing Mail (SMTP) server for notifications ...............
   
   -----------------------------------------------------------------
   Do you wish to continue? [yes(Y)/no(N)]: Y
   Aug 27, 2008 11:43:28 PM oracle.sysman.emcp.EMConfig perform
   INFO: This operation is being logged at /export/pspp/oracle/cfgtoollogs/emca/test/emca_2008-08-27_11-43-09-PM.log.
   Aug 27, 2008 11:43:31 PM oracle.sysman.emcp.EMReposConfig dropRepository
   INFO: Dropping the EM repository (this may take a while) ...
   ...
   ...

You are done. As simple as that.
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