FILE_STATUS_TEMPORARY
in includes/file.inc
A files status can be one of two values: temporary or permanent. The status for each file Drupal manages is stored in the {files} tables. If the status is temporary Drupal's file garbage collection will delete the file and remove it from the files table after a set period of time.
If you wish to add custom statuses for use by contrib modules please expand as binary flags and consider the first 8 bits reserved. (0,1,2,4,8,16,32,64,128)
<?php
define('FILE_STATUS_TEMPORARY', 0);
?>