The Virtuoso Data Access Clients ODBC, JDBC, ADO.Net, OLE DB, Sesame, Jena and Redland as of Release 6.1 and above support round robin connections to Virtuoso server instances enabling server fail over, load balancing and fault tolerant connections to be performed across multiple server instances configured in a cluster or as separate server instances.

Fail over connections are enabled by specifying a comma delimited list of servers to failover to, in the "Host" or 'Server" connect string attribute, with the list being worked through in the order presented to determine which Virtuoso Server instance is used. A Round robin (load balanced) connection can be configured by adding the connect string attribute "RoundRobin" = [True | Yes | False | No], in which case the server for the connection is chosen at random from the comma delimited provided as for a Failover connection above.

Example connect strings for Virtuoso ODBC, JDBC, ADO.Net and OLE DB driver/providers are provided below. The Virtuoso Sesame and Jena providers which make use of the JDBC driver and Redland Provider which makes use of the ODBC driver, would simply make use of a suitably configured JDBC or ODBC connect string to enable Failover or Round Robin connections to be made with them.