Hi Saba,

I went thru metalink and found the following document which might be of help to you

Goal: How to Troubleshoot Management Server Startup Errors

Fact: Oracle Enterprise Manager
Fact: Oracle Management Server

Change: NOTE ROLE: EM CONSOLE ERROR
The Oracle Management Server (OMS) is the middle-tier of the Enterprise
Management (EM) Framework. If the OMS process is not running, the EM Console
will not start because it must make a connection to the OMS. If this
connection attempt fails for any reason, the EM Client will receive the error:

VTK-1000: Unable to connect to Management Server
Please verify that you have entered the correct name and
status of the Oracle Management Server
OK


Fix: If the OMS will not start successfully, follow this checklist:

1. Start the OMS from a command prompt by typing:
oemctrl start oms

2. Look for errors. They will either be displayed to the screen or
captured in the sysman\log\oms.log file.

NOTE: On NT: 2140 and 1067 are common errors displayed to the screen.
Check the oms.log file for a more descriptive error.

3. The solution will vary depending upon the actual error encountered.

********************************************************************************
Some possible errors captured in the oms.log might be:
********************************************************************************

(Links are listed under Reference Documents)

1. The EM Repository Schema is not created. (ora-1017)
2. The EM Repository Schema objects have been dropped. (ora-942)
3. The EM Repository Database is down or not accepting connections.
4. The Repository Password is incorrect in omsconfig.properties file.(ora-1031)
5. The OMS cannot resolve the EM Repository's TNS alias. (ORA-12154, ORA-12203)
6. The OMS cannot resolve the EM Repository Server's hostname. (ORA-12545)
7. The OMS is not installed correctly. (ORA-12154; VXA-2017)
8. The EM Repository version is not compatible with the OMS version.
9. The EM Repository Database is still starting up. (VXA-2018,ORA-01034)
10. The EM Repository Database rollback segments are offline. (VXA-2019,VXA-2021)
11. The EM Repository Database's Node Has Been Given a New IP Address.
12. The EM Repository Database Is Moved To A Different Node Without Updating Files
13. The omsconfig.properties file might be missing (NT - 203). No log will be generated.
14. The omsconfig.properties file was created with security option enabled.
15. The OMS was not started with the correct syntax. (VXA-2008)


********************************************************************************
Reference Documents
********************************************************************************

1. [NOTE:114767.1] Starting Management Server Fails with NT error 2140 - ORA-1017 When Repository Schema is Missing
2. [NOTE:114765.1] Starting Management Server Fails with NT error 2140 - ORA-942 When Repository Schema Objects Are Missing
3. [NOTE:1066209.6] Starting Management Server Fails with ORA-12224 When Repository Database's Listener Is Not Running
4. [NOTE:107776.1] Starting Management Server Fails with NT error 997, (ORA-1031)
When omsconfig.properties File Does Not Contain Repository Logon Credentials
5. [NOTE:111293.1] Starting Management Server Fails with ORA-12154 in OMS.LOG
6. [NOTE:107200.1] Starting Management Server Fails with ORA-12545 When Repository Database's Hostname Is Unreachable
7. [NOTE:1072972.6] Starting Management Server Fails with VXA-2017 and ORA-12154 When OMS is not installed correctly.
8. [NOTE:104926.1] Starting Management Server Fails with VXA-2019, VXA-2021 When OMS Version Doesn't Match Repository Version
9. [NOTE:105740.1] Starting Management Server Fails with VXA-2018, ORA-1034 When
Repository Database Is Also In The Process Of Starting
10.[NOTE:111563.1] Starting Management Server Fails with VXA-2019, VXA-2021 When
Repository Database Rollback Segements Are Offline
11.[NOTE:108668.1] Starting Management Server Fails with ORA-12225 After Repository Database Node Gets New IP Address
12.[NOTE:124497.1] Starting Management Server Fails with NT error 1075 When Repository Database Is Moved
13.[NOTE:105417.1] Starting Management Server Fails with NT error 0203 When omsconfig.properties File Missing
14.[NOTE:107776.1] Starting Management Server Fails With NT error 997 When Security Option Is set in EMCA.
15.[NOTE:105419.1] Starting Management Server Fails with VXA-2008 When OMS Is Not Start With Correct Parameters


General Information:
--------------------
[NOTE:107241.1] QUICKSTART GUIDE: Enterprise Manager 2.1
[NOTE:113793.1] Overview Of The OEMCTRL Script Used To Control the Oracle Management Server
[NOTE:69522.1] How To Activate Logging and Tracing for Enterprise Manager 2.x Components
[NOTE:107235.1] How To Start The OMS From Windows NT Dos Prompt
[NOTE:105424.1] How To Create The Management Server Service on Windows NT

PS : You can refer to the corresponding document depending on the log file which will be created

Regards