[Exist-open] DB writes possible while backup is in progress?

[Jo C. <Jo....@ha...>]

Dear list,

I have been asked to review the behaviour of exist backups.

At https://exist-db.org/exist/apps/doc/backup, it says that prior to
running the backup, the following steps are taken:

   - Wait for all pending transactions to complete.
   - Enter protected mode. No new transactions will be allowed. Concurrent
   requests by other clients will be blocked and added to the internal queue.

Experiments suggest that, while a backup is in progress, database writes
are still in fact permitted.  I did a manual trace through the code at
exist-core/src/main/java/org/exist/backup/Backup.java and didn't see any
code that places a lock on the database or sets the db as read-only (as the
system will do when disk space drops below the minimum).

Has anyone looked at this situation?  Is the documentation inaccurate here?

Best regards, -- Jo