Drupal 7 | Preserve file after entity_wrapper unset?

Question is quite simple: How to preserve file on server and in file tables, so its fid is still valid after unsetting/changing value with entity wrapper?

$ewrapper = entity_metadata_wrapper('node', $sourceNode);
unset($sourceNode->field_image[$sourceNode->language][0]);
$ewrapper->save();

Now the related file is deleted as soon as the above is called. Same happends if I use:

$ewrapper->field_image->set($newImage);

In this case I need to keep the old image.

Thanks for your help guys!

I think that you should change file status from FILE_STATUS_TEMPORARY to FILE_STATUS_PERMANENT. Check out this answer here:

https://api.drupal.org/comment/23493#comment-23493

Basically, there is no file_set_status() function, like Drupal 6 had one, but now this code should do the same job:

  // First obtain a file object, for example by file_load...
  $file = file_load(10); 

  // Or as another example, the result of a file_save_upload...
  $file = file_save_upload('upload', array(), 'public://', FILE_EXISTS_REPLACE);

  // Now you can set the status
  $file->status = FILE_STATUS_PERMANENT;

  // And save the status.
  file_save($file);

So, you load file object one or another way, change it's status property and save object back again.