Troubleshooting DbConsole Error - OC4J Configuration issue

Error Description:
emctl start dbconsole
fails with the exception:
EM Configuration issue. /u01/app/oracle/product/10.2.0_64/db_1/_

Solution of The Problem:
First we need to determine whether the server use dynamic IP or static IP. There are two different solutions for these two.

1)If Server is configured with dynamic IP Address:
a)In the Loopback adapter configure and assign a dummy static address.
b)Then in the "hosts" file, add an entry associated with this dummy static IP address and map that to the machine name associated with the system through the system properties.
c)Configure the loopback adapter to be the primary network adapter on the system.
d)Now, any call to get the IP address of the system will return the dummy static IP associated with the loopback adapter. In call to get the hostname associated with this dummy IP address will return the real machine name, since this was associated with the IP address in the hosts file.
e)Also, any call to get the hostname will also return the machine name since the loopback adapter is the primary network adapter.

Suppose in Windows,

a). In the SYSTEM DRIVE:\WINDOWS\system32\drivers\etc\hosts file the following entry should be present for the node :

127.0.0.1 localhost hostname.domainname hostname

b). Set this environment variable to the hostname of the machine, from a command prompt:

For 10.1,
cmd> set EMHOSTNAME=

For 10.2,
cmd> set ORACLE_HOSTNAME=

c). Start the dbconsole now from the same window
cmd> set ORACLE_HOME=ORACLE_HOME of the 10G database
cmd> set ORACLE_SID=SID of the 10G database
cmd> cd %ORACLE_HOME%\bin
cmd> emctl start dbconsole

d).If the existing files/directories in the %ORACLE_HOME%\oc4j\j2ee\OC4J_DBConsole_hostname_SID and %ORACLE_HOME%\hostname_SID have the IP address instead of the hostname then recreate DBControl.

2)If Server uses static IP address

a)Check the hosts file entry:
On Windows, the HOSTS file is under $WINDOWS\system32\drivers\etc
On Unix systems hosts file is under /etc

The file should have the IP address followed by the fully qualified hostname.domain name, and then a short hostname or alias.
For Example,

192.168.1.2 hostname.domainname hostname

b)Check hostname and IP Address:

On unix, $ hostname $ifconfig -a
On Windows >ipconfig /all

>ping 192.168.1.2
>ping hostname.domainname
>ping hostname
>nslookup 192.168.1.2
>nslookup hostname.domainname
>nslookup hostname

c). Check if directories

/_
/oc4j/j2ee/OC4J_DBConsole_

exist and have correct permissions for the same user who has installed the software.

If they does not exist then recreate dbcontrol.
You can do it by,
$emca -deconfig dbcontrol db -repos drop
$emca -config dbcontrol db -repos create
I have shown how to drop , create and recreate dbcontrol in topic,

How To Drop, Create And Recreate DB Control In 10g Database

d)Ensure ORACLE_HOME and ORACLE_SID is set properly.

Related Documentation:
How to create and recreate DBcontrol