Memory is allocated during reload to hold loaded data records and cache results of data value processing.
The amount of memory required for the loaded data depends on the nature of the data, in terms of number or rows and symbols required to represent the data. See How is data stored in QlikView?
for more details on how data is stored in memory. If the loaded data is manipulated during load, this will lead to additional memory allocation to hold cached results of the aggregation or manipulation. After finished reload the cached values related to the reload are purged from memory.
In server side reload the reloaded data model is stored from memory to file, followed by the data in memory being purged. After this there is no remaining memory allocation related to the reload. The application will be loaded into memory again once opened by the server or reloaded again.
In desktop client the reloaded data model remains in memory as long as the application remains open in the client. If the data model size increased during reload, the memory allocation can appear larger after reload compared to before reload.