When you have an established connection to ArangoDB, the current database can be changed explicitly using the db._useDatabase() method. This will switch to the specified database (provided it exists and the user can connect to it). From this point on, any following action in the same shell or connection will use the specified database, unless otherwise specified.
Note: If the database is changed, client drivers need to store the current database name on their side, too. This is because connections in ArangoDB do not contain any state information. All state information is contained in the HTTP request/response data.
To connect to a specific database after arangosh has started use the command described above. It is also possible to specify a database name when invoking arangosh. For this purpose, use the command-line parameter --server.database, e.g.
> arangosh --server.database test
Please note that commands, actions, scripts or AQL queries should never access multiple databases, even if they exist. The only intended and supported way in ArangoDB is to use one database at a time for a command, an action, a script or a query. Operations started in one database must not switch the database later and continue operating in another.