On a recent flight, I wanted to read some PDFs I’d put in my iCloud Readdle “Documents” app folder. They were listed Documents’ iCloud folder, but when I tried to open them, it said they needed to be downloaded, and on the plane I had no Internet, so I couldn’t do any of that reading.
Apparently iCloud (or the iPad) is doing some “optimizing,” deleting files I haven’t opened in a while. Is that’s what is happening? If so, is it because the iPad or iCloud is low on storage space? Are file just removed after some period of not being opened?
Is there a way to insure iCloud files are never removed without my OK?
A clarifying question as I do not use Readdle, are things configured to store the PDFs on iCloud or to backup the PDFs in iCloud?
If it is the former then it would make sense that they would need to downloaded, as they are stored in the cloud. And as @winmaciek notes you would need to save them locally to a folder in Files on your iPad to be able to access them when offline.
If it is the latter then I’d be concerned because that isn’t really back up then, as there would only be one copy of the file, that on iCloud.
The iPad probably did some optimizing as it was low on storage space. This is what iOS does when it’s low on storage space as it assumes you will be able to re-download files from the cloud at some point.
In the Documents app, if you want to be sure you have files available offline, you should download them into the Downloads folder (not the iCloud Downloads but the Downloads folder provided in the Documents app). However you should then keep in mind that these are no longer syncing to the cloud, but it is useful when expecting you’ll be offline.
For other cloud services like OneDrive etc. the Documents app will let you sync any cloud folder locally to the iPad (and will continue syncing it two-way when you come back online) but it does not support that for the iCloud.
I have similar questions, I can never understand how iCloud works on mac and iPad , iPhone etc. It seems not reliable and files are not accessible when I want them. Photos are most reliable but Notes, Books, iCloud drive are not
iCloud is trying to make it easy for people by managing the storage for you and removing files that you haven’t accessed in awhile. For power users, this is less than ideal. You should use the “On My iPad” folder in Files to keep a copy of the files you know you will need on the plane. Then you will have to remember to remove them when you no longer need them offline.
That’s precisely what I had in mind when I mentioned “On My iPad”.
The whole problem seems to vary between Apple’s apps. Files and books are regularly purged automatically, but videos are not. There’s definitely been a couple of times when a book (ot purchased on iBooks) that I had explicitly set to be downloaded either wasn’t actually downloaded or became purged between the gate and the takeoff. Extremely annoying, though it seems to be less common these days.
I find it especially annoying with Photos. Often I take or download a photo and just minutes later I want to use it further. Already it has to be downloaded again. It really should keep a few of the latest pictures ready all the time.
The difference is that the Downloads folder in Readdle’s Documents app belongs to that app (and this is how iOS sees it), and the On the iPad section belongs to iPadOS itself.
We don’t know enough to answer the question of what makes iOS/iPadOS go and remove things when it is low on storage space, but presumably, the files in any of these two folders will not be immediately deleted (those in On the iPad because they have no cloud copy, and those in Documents’ Downloads folder as they belong to an app, though this can of course not be guaranteed if you are really low on storage space) but from what I have experienced iOS will clear full-resolution photos, books, synced folders and files from iCloud Drive, Apple Music downloads etc. before removing any app data or locally stored files.
iOS is very aggressive when it even begins to approach low storage space, so make sure you always have a copy available in the cloud.
There is no published algorithm. I think it generally prioritizes whatever is used frequently and what user has asked to be downloaded. Sometimes it’s too aggressive with purging local copies, especially when the device is low on disk space.