"Data Source Is Invalid" Error Message Opening Performance Log File


When you attempt to open a log file in System Monitor (Perfmon) on a Windows 2000-based computer, you may receive the following error message:

Data source 'Filename.xxx' is invalid. The log file contains fewer than two data samples.


The error message occurs if the log file does not contain information for at least two data points. System Monitor requires at least two data points to use as end points. Common causes for this behavior include:

  • You start and stop a log within 15 seconds. There is not enough time for information for two data points to be written.
  • The log file is very small (around only 20 KB).
  • The log file is corrupted.


Check the logging interval and make sure that at least two points are being written. If the log file is only 10 to 30 KB in size, the log may contain only one data sample even if it ran for some time.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

Artikelnummer: 264134 – Letzte Überarbeitung: 28.02.2007 – Revision: 1