Clearing and reloading a list increases the structural changes within a model and will increase the likelihood of a of model save, thus increasing the import time. It also removes pre-allocated memory block designed to increase efficiency. Use a unique key to update to values rather than delete and re-load. Also consider adding a TRUE field to the data source which will allow you to know which records have been imported
Best Practices articles
Data Hubs Purpose and Peak Performance
Pre-Allocation in Lists and Impacts to Model Performance
Rule 1.05-10 Never delete list and reload the list as daily occurrence. Using a unique key to update to values rather than delete and re-load. It goes against P & N elements of PLANS.
Here is how it was done in Pre Planual Era: When we had to delete the transactional data & reload the data we used to delete/wipe out the entire list items of the lists
What is wrong with this method? There are a lot of disadvantages
Here is how it should be done in Planual Way: All the transactional data should flow into modules and NOT lists, which is a Thumb Rule.
Now if your client operates in such a way that you have to delete the transactional data then you delete it from the modules without touching the list items. You can do it by creating a process which will wipe out the data first and then reload it back
Now there can be many scenarios where you need to load data for all historical periods (i.e., restating the history) or load data for few periods (i.e., current month and previous month). These all can be tackled through filters and having one saved view for each scenario
Ideally what should happen is that only the updated/changed data should make its way to Anaplan Data Hub and not the entire data set which probably may remain unchanged. Two ways to achieve this -