Missing attachments
I use Zotero Storage with a 6GB plan and my current usage is at 67%. Frequently I discover that an attachment is missing from my local storage. In my Web Library on Zotero Storage, the file name appears in the attachment panel but the interface does not provide an option to download it, indicating that the file does not exist on the remote server, either. Normally when this happens, I just download the file again and reattach it to the reference, but this isn't a stable solution. Can anyone offer help with debugging this problem?
What you describe isn't possible with Zotero itself. If you add a file on one computer, the file will always exist there, unless you or something else deletes it from outside of Zotero. There's literally no code in Zotero that would delete a file separately from the attachment item. (A future version of Zotero will make it possible to configure how long local copies of files should be kept in order to save disk space, but that's not out yet, and it would only apply to files that had been uploaded in any case.)
If a file doesn't exist, and it also doesn't exist online, it was almost certainly added on another device. It looks like you have used the iOS app, which counts as a "computer" in this case. So you'd want to check the files there.
(You also appear to have been using ZotFile in the past. We can't vouch for anything ZotFile might have done.)
https://www.zotero.org/jsdodge/items/Y5WUWMCG/item-list
Thanks for clarifying the way things work. I just checked on my iOS device and the above file isn't there, either.
It's entirely possible that something other than Zotero caused this—I'm just looking for a way forward. I encounter missing attachments infrequently, so it's possible that they were lost at a discrete moment in the past and the problem is not ongoing. I'll remove ZotFile, for starters. Is there a way that I can purge the missing attachment links while leaving the parent references intact? If it's not an ongoing problem, then I can just reattach the PDFs as needed.
Did you use "Purge Storage in My Library" from your storage settings online at some point?
I believe those are the only two possibilities for the state of the file online — details about the file exist, but the file itself doesn't.
That file hasn't been updated in 2019, so this might have been something you did years ago.
At this point, I’m less concerned with how it happened and would like to know if there is a way to automatically find and delete stale file references. Ideally, I’d back up my local library, purge the stale references from the remote, then overwrite my local library with the remote copy. I’d keep the backup in case the remote is missing references to files that are actually in my local library. Is this possible?