Not able to execute drush rr command

Hi ,
Exploring drush and try to execute "drush rr" / "drush @my_site_alias rr" command but got following error

"You need to specify an alias or run this command within a drupal site."

I have tried to find solution by google it and i perform following steps

1. Registry Rebuild
$ drush dl registry_rebuild

2. Clear cache
$ drush cache-clear drush

3. Create alias for my local website by creating file names ".aliases.drushrc.php" in ~/.drush directory

Still i am getting above error. Please anyone let me know what i missed here

Thanks....