Oracle Forms

I need to know if a file exists on a network drive.

webutil_file.file_exists works if i try to check a local drive but when i try to check a network drive, it returns FALSE

This line of code works perfectly
w_existe_arq := webutil_file.file_exists('H:\fiscal\sif\teste.txt');

This line doesnt work, return FALSE
w_existe_arq := webutil_file.file_exists('/comum/fiscal/sif/teste.txt');

Ive already tried w_existe_arq := webutil_file.file_exists('//comum/fiscal/sif/teste.txt');

and it didnt work too

Do you guys know how can i check if a file exists on a network drive ?

Thx in advance