hi
I installed oracle 10g in linux installation is successful
On of my application try to access the oracle database
I got this message

Database server for oracle database on localhost does not responding
Possible causes for this problem includes:
1 the database user ID or password is in correct,
2 the database server is not installed in specified location or
3 the database server is not running

I donít know how to run the database server

Thanks in advance