Changes to the source systems from which the data warehouse is built can be detected to a limited degree. The menu option Validate > Validate Load Table Status enables a comparison between load tables and the source tables from which they were built. This comparison is not available for flat file or script-based loads. A Load table or group of load tables is selected, and the results are displayed in the middle pane. An example screen from a Load table validation is as follows:
The tables load_budget and load_forecast are Windows file loads and as such, cannot be validated.
If a table shows additional columns in the source table; such a scenario will not cause problems for the continued operation of the data warehouse. It simply means that more columns are present in the source table than have been loaded into the data warehouse. This may have been the result of an initial partial selection or as a result of new columns. Further investigation of the source table would be required to ascertain if there was new information available.
The table load_state reflects a problem for the continued operation of the data warehouse. The source table does not have a column that was previously identified as having come from that table. This will probably cause the load of that table to fail. This scenario would also require an investigation into the source table. The resolution may be to delete the column. The potential impact on later tables (Dimension, Stage, and Fact) and procedures in the data warehouse can be ascertained by using the right-click menu of a Load table.