QVD – QlikView Data File is a very powerful feature of QlikView.
QVD is a native QlikView format. It can be only written or read from QlikView.
You can connect to the data source and export data in the table in a QVD.
Advantage of QVD
– Once data is exported in the QVD you don’t have to connect to database. Your data will reside in QVD.
– Reading from QVD is 10-100 times faster than reading from Data sources.
– Consolidating data from multiple data sources and databases.Create multi layer QVDs to create a robust data model.
– Incremental load can be implemented only by using QVDs
Storing Data in QVD
Table data can be stored in QVD by using ‘Store’ ‘into’ commands
QVD file will be stored in the specified location .
Reading from a QVD
You can read data from a QVD just like reading from a table.
QVDs can have calculations and expressions. You can create and read from multiple QVDs and they will be associated similar to tables.
Once data is loaded in the QVDs you don’t have to stay connected to data source thus reducing load on the database servers.Only time you will connect to database is when you need to refresh your QVD data with the updated data in the database.
You can schedule task on the QlikView server to reload your QVDs. To schedule tasks on the server, you need to deploy your dashboards on the QlikView Server.
Please visit my blog Deploying QlikView dashboard on the Server for more details on deployment.
QVDs are very useful when performing Incremental load. Please visit my blog Incremental Load in QlikView to learn more details.