TYPO3 occasionally throws the following error message when attempting to connect to the MySQL database, blocking the operation of the website. The error also occurs when reporting is set to Production mode in the install tool.
Uncaught TYPO3 Exception: #1: PHP Warning: mysqli::real_connect(): (HY000/1040): Too many connections in […]/typo3_src-6.2.13/typo3/sysext/core/Classes/Database/DatabaseConnection.php line 1199 | TYPO3\CMS\Core\Error\Exception thrown in file[…]/typo3_src-6.2.13/typo3/sysext/core/Classes/Error/ErrorHandler.php in line 101
The error is produced when there are too many concurrent database connections open, and appears to be an issue when running the CMS in a shared hosting environment. This isn’t a new issue, but one which has cropped up from time to time ever since version 4 of the CMS. The key is to ensure that you disable persistent database connections, as advised by Dmitry Dulepov way back in 2008. Simply set
TRUE in LocalConfiguration.php.