public String getSQLServerInstance() throws GuacamoleException {
        return getProperty(
            SQLServerGuacamoleProperties.SQLSERVER_INSTANCE
        );
    }
Returns the instance name of the SQL Server installation hosting the
Guacamole database, if any.  If unspecified it will be null.

@return
    The instance name of the SQL Server install hosting the Guacamole
    database, or null if undefined.

@throws GuacamoleException
    If an error occurs reading guacamole.properties.
extensions/guacamole-auth-jdbc/modules/guacamole-auth-jdbc-sqlserver/src/main/java/org/apache/guacamole/auth/sqlserver/conf/SQLServerEnvironment.java