I have found the information:
https://learning.health.org.kw/admin/settings.php?section=sessionhandling
I also found the following information in Moodle.org:
https://docs.moodle.org/26/en/Session_handling
However, I am confused about how to configure correctly config.php according to that page. We don't use a memcached server so my understanding is that the memcached configuration options in config.php are not applicable.
Are the options of 'Files' and 'Database' applicable:
$CFG->session_handler_class = '\core\session\file';
$CFG->session_file_save_path = $CFG->dataroot.'/sessions';
$CFG->session_handler_class = '\core\session\database';
$CFG->session_database_acquire_lock_timeout = 120;
The information says that the database driver was used for Moodle 2.0-2.5 installations, but not for Moodle 2.6