The same document/app takes more time to open (up to 3-5 times more) when Section Access (SA) is applied. This occurs especially if the file is large and if SA performs many selections (reductions) on it.
QlikView, all versions
Qlik Sense Enterprise, all versions
Section access will always need some additional overhead to evaluate the authorization and to perform a data-reduction.
When a user opens an app/document with SA, a table is created in-memory with all of the reduction fields applied. The data is then reduced, hypercubes are re-calculated as needed, and then the application is displayed to the user. The higher the SA table complexity, the longer this process may potentially take as the reductions needed increase in complexity. These reductions add to the cache, which may not get flushed if not needed by the OS due to working set reaching upper limit.
It is possible to mitigate the problem optimizing the document /app:
Optimize the Data model and especially the objects in the GUI.
Remove objects from the landing sheet (for QlikView).
Move complex expressions to the script whenever it is possible.
Avoid tables with large quantity of data.
Disable data-compression under Settings > Document properties > General. This option helps to save some storage space in the disk, but it costs time and resources by decompressing.