If we are getting Error while running reports.

 Error:

 REP-0004: Warning: Unable to open user preference file

 Solution:

 Make sure the file prefs.ora is located in your "home" directory  If it is not, change the directory or filename as appropriate.

 Copy $ORACLE_HOME/tools/admin/prefs.ora to $HOME

 If error is not solved after copy the prefs.ora also then you have to check privileges.

 After changing privileges bounce application services.