This section describes breaking changes for the Neo4j DBMS.

1. Multiple databases

From version 4.0 onwards, Neo4j supports the management of multiple databases within the same DBMS. The metadata for these databases, including the associated security model, is maintained in a special database called the system database.

A default installation of Neo4j contains two databases:

  • system - the system database, containing metadata on the DBMS and security configuration.

  • neo4j - the default database. A different name can be configured before starting Neo4j for the first time.

2. Database naming rules

With the introduction of multiple databases, the rules for naming a database have changed. For example, it is no longer possible to use an underscore in a database name. For a full list of naming rules, please see Operations Manual v4.0 → Administrative commands.

3. Embedded layout

To support multiple databases in an embedded layout, the store files, transaction files, and log files no longer reside in the base directory. Instead, files are separated per database into separate directories. For more information, see Operations Manual → File locations.