Alain Raap

I already inspected that folder, the mdl_backup_controllers table showed the 54 failed backups
with status 800, in the backup logs the error I found there is dmlwriteexception, so it's a database
problem. To be continued..

That's the problem, all failed backups end with a ' Exception: dmlwriteexception' and status 800. I can't find the real errors in the logs of Moodle.
I have 'debugsqltrace' activated with option "Show complete stacktrace" in the admin settings.
The table 'mdl_log_queries' also doesn't contain log records with these write errors after I changed the settings in config.php

Hi Ken,

We're running MariaDB 10.5 on RHEL8, we're having more problems with backups at the moment, also the automated backup who gives database errors.
I'm investigating what's going wrong at that point, and made some changes in the Moodle config file for debugging. Nadav Kavalerchik gave me this tip, add these two parameters to the CFG->dboptions array:
'logslow' => 5,
'logerrors' => 1,
and in table log_queries the errors and stacktraces are being logged. Tomorrow I hope to see the results of this configuration change.

Severin, I tested this function several times and it doesn't work as expected, several times the copy finishes without problems, and another try I got this
error "Potential coding error - existing temptables found when disposing database. Must be dropped!". The backup files are still in the temp backup folder and the restore doesn't proceed anymore and is frozen with the message that it is running (for an endless time).