Do you understand what incremental load is? I suggest that you read the QV reference manual - it has a good explanation.
Perhaps you are looking for a partial load. This allows you to add to or replace individual tables in your data model without reloading all the tables. Partial load uses the ADD and REPLACE modifiers on the load statement that will affect the loading when a partial load is requested (from the desktop client, server task option or command line switch).
Incremental by definition means that you only load the changed data from your previous load.
QVD is the preferred choice of data storage, as it is an optimized file format for QlikView and Qlik Sense. Technically you could find other file formats to hold the current data, but other formats would decrease performance.
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You can implement Incremental loading by using CSV or Txt file also. We need to store previous data somewhere to implement Incremental Loading, for this QVD is the best choice, because the loading is around 100X times faster when compared to Database or other sources. In QVD we will store the past data and during reload we will get only the latest data from Source and concatenates this to the previous data in QVD.
Hope this explanation helps you.
Depending on the size of the tables it might be worth having a look at the buffer statement if you want something simple:
buffer (incremental) LOAD * FROM MyLog.log;
This creates a qvd file for you.
Have a look in the qlikview desktop help for more details.