The server has built-in support for different databases. You can query the available databases by viewing the expected values for the `db` configuration option. The following table lists the supported databases and their tested versions.
By default, the server uses the `dev-file` database. This is the default database that the server will use to persist data and
only exists for development use-cases. The `dev-file` database is not suitable for production use-cases, and must be replaced before deploying to production.
For each supported database, the server provides some opinionated defaults to simplify database configuration. You complete the configuration by providing some key settings such as the database host and credentials.
The server uses JDBC as the underlying technology to communicate with the database. If the default connection settings are insufficient, you can specify a JDBC URL using the `db-url` configuration option.
Be aware that you need to escape characters when invoking commands containing special shell characters such as `;` using the CLI, so you might want to set it in the configuration file instead.
Unicode support for all fields depends on whether the database allows VARCHAR and CHAR fields to use the Unicode character set.
* If these fields can be set, Unicode is likely to work, usually at the expense of field length.
* If the database only supports Unicode in the NVARCHAR and NCHAR fields, Unicode support for all text fields is unlikely to work because the server schema uses VARCHAR and CHAR fields extensively.
Otherwise, characters are limited to those contained in database encoding, which is often 8-bit. However, for some database systems, you can enable UTF-8 encoding of Unicode characters and use the full Unicode character set in all text fields. For a given database, this choice might result in a shorter maximum string length than the maximum string length supported by 8-bit encodings.
Unicode characters are supported in an Oracle database if the database was created with Unicode support in the VARCHAR and CHAR fields. For example, you configured AL32UTF8 as the database character set. In this case, the JDBC driver requires no special settings.
If the database was not created with Unicode support, you need to configure the JDBC driver to support Unicode characters in the special fields. You configure two properties. Note that you can configure these properties as system properties or as connection properties.
Unicode characters are supported in a MySQL database if the database was created with Unicode support in the VARCHAR and CHAR fields when using the CREATE DATABASE command.
Note that the utf8mb4 character set is not supported due to different storage requirements for the utf8 character set. See MySQL documentation for details. In that situation, the length restriction on non-special fields does not apply because columns are created to accommodate the number of characters, not bytes. If the database default character set does not allow Unicode storage, only the special fields allow storing Unicode values.
Unicode is supported for a PostgreSQL database when the database character set is UTF8. Unicode characters can be used in any field with no reduction of field length for non-special fields. The JDBC driver requires no special settings. The character set is determined when the PostgreSQL database is created.
Because cluster nodes can boot concurrently, they take extra time for database actions. For example, a booting server instance may perform some database migration, importing, or first time initializations. A database lock prevents start actions from conflicting with each other when cluster nodes boot up concurrently.
The maximum timeout for this lock is 900 seconds. If a node waits on this lock for more than the timeout, the boot fails. The need to change the default value is unlikely, but you can change it by entering this command:
Keycloak uses XA transactions and the appropriate database drivers by default. Certain vendors, such as Azure SQL and MariaDB Galera, do not support or rely on the XA transaction mechanism. To use Keycloak without XA transaction support using the appropriate JDBC driver, enter the following command:
