Solution:

Although the scan time is not a property of any driver object, it is important to know how it affects driver throughput and data integrity. Whether using FIX View, or a Visual Basic Client, the rate at which the data is being read or written is usually referred to as the scan time. Example Assume a Visual Basic Client has a timer function that calls the I/O Server's ReadData method. The ReadData interval is a property you can configure in a Visual Basic Timer. If the interval is set to 30 seconds, the Visual Basic Client calls the ReadData method every 30 seconds and accesses data every 30 seconds. The data returned from the ReadData method is directly from the I/O driver memory. The data in memory updates only when the driver polls. The ReadData method does not poll for data and waits for a memory update before returning a value. Therefore, having a scan time slower than the access time always returns old data and the driver flags the data quality as NO_DATA. To resolve this problem, select a scan time that is faster than the access time and enter an access time that is slower than the primary poll time. For example, if you select a scan time of 30 seconds, you could use an access time of 45 seconds and a primary poll rate of 15 seconds. NOTE: Specifying an access time that is faster than the primary poll time forces the driver to poll at the access time interval; however, the data received is always old and is marked with the NO_DATA quality flag. Similarly, entering a scan time that is slower than the access time also results in old data. The data scanned each interval is as old as the access time minus the scan time and is marked with the NO_DATA quality flag.