Does the server has a "journal" of file/folder modifications?

This is best described with a scenario:
There are two users on a nextCloud server. One is working nearly every day, modify, delete, create files and folders. The second one is on a sabatical and the PC with the nextCloud client is off for months - let’s assume 6 months.

My question for this scenario: A lot of things happen in 6 months! The server need to tell the second client (when it comes back after sabatical) what was changed (created, deleted, moved/renamed) to sync that. Does the server keep a journal for that?

If so is the size of the journal, the number of its entries or the age of entries limited? Are there setting parameters to modify that limitations?

Background: I use different nextCloud and ownCloud instances with multiple users. From time to time it happens that files/folder that where deleted or renamed long ago (e.g. 2 months) appear again on the server and are synced to all clients.
Because of the complex user scenario and the none-IT-users it is hard to get down to the root of the cause and problem. But I hypothesize that a user with a long-time-disconnected client (e.g. after a sabatical of 6 months) reconnects to the cloud and sync all the old stuff back.

If there is no journal: How does the second (long disconnected) client know that its local folder “01. Foobar” is the same as the servers “1 foobar”? The first client renamed “01. Foobar” to “1 foobar” - long ago. But in my real situation “01. Foobar” is synced to the server as a new folder. And from that point on both folders “01. Foobar” AND “1 foobar” exist on the server.

my understanding of this is limited but I think we use etags and no journal at all

Dear Christoph,
thank you for your reply.

ETags are interesting. I know that technic from Newsfeeds (RSS, Atom) because I am a developer of a Newsfeed reader and have to deal with servers/generators (miss)using ETags.
I still do not fully understand how servers use and generate ETags. But in the area of newsfeed generators some etags ignored/useless. Some ETags expire after (e.g.) 20 minutes or some days.

From my experience there can something go wrong with ETags also.
How is an ETag involved in my scenario with a renamed folder?

it’s simple. the etag changes when contents change. if oyu change a file, its etag changes. but also the one of all parents. so the sync client starts to compare its etag in the root directory and from there it can build a tree with the diffs

that is my understanding, I might be wrong

Ok, but in that process there must be a history (or journal) of etags.

The question is how big/long can it grow.

I might be wrong because, again, my knowledge here is limited but as far as I understand this etag is a simple attribute of every entry in Nextcloud’s file index -> the table oc_filecache. That one can grow large if you have many files, yes.

Is there anyone of the core devs reading this and can bring more light into that topic?