UTL_FILE Error

I was getting the below error while working on a small program using UTL_FILE.

ORA-29280: invalid directory path
ORA-06512: at "SYS.UTL_FILE", line 41
ORA-06512: at "SYS.UTL_FILE", line 478

I have been banging my head on what could be the possible cause for this error. Because I created the directory and it has all the read write permissions on it.

Finally after some goggling I found the issue was because I was passing the directory names in lower case. Till now I was under the impression that Oracle would take lower case parameter as well. Well now I know that I need to pass the directory name in upper case at least while executing the UTL_FILE package.