SQL & PL/SQL

I need to read/write a file from/to the operating system through PLSQL Package. I used UTL_FILE package to do the same. In the application server the utl_file_dir(/usr/tmp in my system) is created as a softlink to database server.
oI want to run this package through the application server. However I am unable to read and write the file to the operating system.

I just wondering it is not reading/opening the file from the server. Please suggest me how to modify my code.