Getting error when uploading file

if your directory architecture is like :
- system
- application :
  -- dir_upload
  -- application_name :
      --- config
      --- controller
      --- models
      --- helper
      --- view

If you want to upload files and record its in directory name 'dir1_upload', path will be 'dir_upload/'.
Use constants APPATH for other configuration or define it as well.
Think to check read/write attributes for your directory too (chmod).