Most OpenStack services use an SQL database to store information. The database typically runs on the controller node. The procedures in this guide use MariaDB or MySQL depending on the distribution. OpenStack services also support other SQL databases including PostgreSQL.
If you see
Too many connections or
Too many open files error log messages on OpenStack services, verify that maximum number of connection settings are well applied to your environment. In MariaDB, you may also need to change open_files_limit configuration.