If you are accessing this page directly without looking at previous post on Web Server log files & basics then my suggestions are that you first go through link
Now by looking at error_log, jserv.log, mod_jserv.log you can find out error message & depending on error message you can try Metalink or Search engine for related error message encountered by others in past.
Most of the issues happen because of change so try to focus on what changed recently ( See if anything related to change is related) . Once you get first page http://hostname.domain:port
then there are few automated tool, scripts to check login issues.
If you don’t get first page even i.e. http://hostname.domain:port then focus on error_log. error_log_pls in Apache/Apache/logs and jserv.log , mod_jserv.log in Apache/Jserv/logs
Once you get first page then when you try to login to application & login is not working then this can be because of number of reasons. In order to understand this you need to understand request flow in Apps . I posted about request flow in August and you can check link at
In order to authenticate your user against database in FND_USER table this request is passed from core Apache Module to mod_pls ( plsql) and it uses few files like wdbsvr.app in Apache/modplsql/conf $CONTEXT_NAME.dbc , tnsnames.ora in 806/network/admin/$CONTEXT_NAME , GUEST user & few other file so focus on these files & directories & see what changed recently. These are quite important and thats why you often these questions in apps dba interview .
Lot of you discussed about difference between GUEST & APPLSYSPUB account ( Both are Public User accounts with very basic access for authentication ). These both are defined in .dbc file under FND_SECURE one for Thin JDBC connection & another for Thick client .
If you can’t login to oracle application by clicking on login link , check if
— dbc file in FND_SECURE is correct.
— APPL_SERVER_ID in dbc file matches with server ID in FND_NODES table against respective Server
— GUEST/ORACLE password is correct & user is not end dated
— APPS password is correct in wdbsvr.app file
— Check http://hostname.domainnamel:port/pls/$SID and see if package fnd_web can ping & you get output in screen from FND_WEB.ping with correct database_id ( and check if there is correct dbc file in FND_SECURE with name $DATABASE_ID.dbc )
There is JSP tool test to find most of issues via
Apart from this if you have Metalink access there is very good note at metalink which you can refer
342332.1 Troubleshooting Login Problems in Oracle Applications 11i (11.5.2
Oracle ACE, Author, Speaker and Founder of K21 Technologies & K21 Academy : Specialising in Design, Implement, and Trainings.