Working with extracts instead of live connections
Nearly all data sources allow the option of either connecting live or extracting the data. A few cloud-based data sources require an extract. Conversely, OLAP data sources cannot be extracted and require live connections.
Extracts extend the way in which Tableau works with data. Consider the following diagram:
Figure 2.19: Data from the original data source is extracted into a self-contained snapshot of the data
When using a live connection, Tableau issues queries directly to the data source (or uses data in the cache, if possible). When you extract the data, Tableau pulls some or all of the data from the original source and stores it in an extract file. Prior to version 10.5, Tableau used a Tableau Data Extract (.tde) file. Starting with version 10.5, Tableau uses Hyper extracts (.hyper) and will convert .tde files to .hyper as you update older workbooks.
The fundamental paradigm of how Tableau works with data...
