Updated three of my KDE clients by terminal (not logged in by display manager/DM) and ran # systemctl restart mariadb.service && mariadb-upgrade -u root -p as stated by pacman and arch-acnnounce. All went fine so far. No client starts or uses a mariadb service. But after logging in at DM and starting Kontact the drama begins: New Mails are shown but no one can be read and journal is showing lots of Jun 28 05:49:17 zotac3 akonadiserver[5774]: org.kde.pim.akonadiserver: DATABASE ERROR: Jun 28 05:49:17 zotac3 akonadiserver[5774]: org.kde.pim.akonadiserver: Error code: "1452" Jun 28 05:49:17 zotac3 akonadiserver[5774]: org.kde.pim.akonadiserver: DB error: "Cannot add or update a child row: a foreign key constraint fails (`akonadi`.`parttable`, CONSTRAINT `parttable_ibfk_1` FOREIGN KEY (`pimItemId`) REFERENCES `pimitemtable` (`id`) ON DELETE CASCADE ON UPDATE CASCADE)" Jun 28 05:49:17 zotac3 akonadiserver[5774]: org.kde.pim.akonadiserver: Error text: "Cannot add or update a child row: a foreign key constraint fails (`akonadi`.`parttable`, CONSTRAINT `parttable_ibfk_1` FOREIGN KEY (`pimItemId`) REFERENCES `pimitemtable` (`id`) ON DELETE CASCADE ON UPDATE CASCADE) QMYSQL3: Unable to execute statement" Jun 28 05:49:17 zotac3 akonadiserver[5774]: org.kde.pim.akonadiserver: Values: QMap((":0", QVariant(qlonglong, 345491))(":1", QVariant(qlonglong, 9))(":2", QVariant(QByteArray, "Return-Path: <receiver@xxxxxxx>\r\nDelivered-To: copyrec@xxxxxxx\r\nReceived: from localhost (localhost [127.0.0.1])\r\n\tby mail.sender.com (Postfix) with ESMTP id 6E9EF624B8;\r\n\tFri, 28 Jun 2019 05:49:16 +0200 (CEST)\r\nDKIM-Filter: OpenDKIM Filter v2.11.0 mail.sender.com 6E9EF624B8\r\nDKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sender.com;\r\n\ts=mail; [...] Jun 28 05:49:17 zotac3 akonadiserver[5774]: org.kde.pim.akonadiserver: Query: "INSERT INTO PartTable (pimItemId, partTypeId, data, datasize, version) VALUES (:0, :1, :2, :3, :4)" Jun 28 05:49:17 zotac3 akonadiserver[5774]: org.kde.pim.akonadiserver: Error during insertion into table "PartTable" "Cannot add or update a child row: a foreign key constraint fails (`akonadi`.`parttable`, CONSTRAINT `parttable_ibfk_1` FOREIGN KEY (`pimItemId`) REFERENCES `pimitemtable` (`id`) ON DELETE CASCADE ON UPDATE CASCADE) QMYSQL3: Unable to execute statement" Jun 28 05:49:17 zotac3 akonadiserver[5774]: org.kde.pim.akonadiserver: Error while handling command CreateItem on connection akonadi_imap_resource_10 (0x55f027a24a20) Jun 28 05:49:17 zotac3 akonadi_imap_resource[1543]: org.kde.pim.akonadicore: Creating/updating items from the akonadi database failed: "Failed to insert new part into database." Jun 28 05:49:17 zotac3 akonadi_imap_resource[1543]: org.kde.pim.akonadicore: Error during ItemSync: "Failed to insert new part into database." ~/.local/share/akonadi/db_data/mysql.err is showing continuously 2019-06-28 6:14:21 10 [ERROR] Transaction not registered for MariaDB 2PC, but transaction is active Stopping akonadi and therefore mariadb, then downgrading to mariadb* 10.3.16-1 helped. Looks like something's not really going together there yet. - Oliver