https://devzone.nordicsemi.com/f/nordic-q-a/60107/nrf52-bootloader---application-data-preserveHi, I am using NRF52832 with secure bootloader to OTA my application in the field using Dual Bank updates and everything is working fine. In my application, I am using FDS library with 12 pages (48kb) reserved for my application data. I was goingen-USTelligent Community 13Tue, 14 Apr 2020 15:30:19 GMThttps://devzone.nordicsemi.com/thread/244509?ContentTypeID=1Tue, 14 Apr 2020 15:30:19 GMT137ad170-7792-4731-bb38-c0d22fbe4515:2be19e0d-1e08-4f76-be7b-fbe5fc6c23deAnkit Bhatnagar<p>Thanks Edvin. Yes I have now set&nbsp;<span>DFU_APP_DATA_RESERVED accordingly to avoid data loss. I just wanted to confirm that I understood was correct :)</span></p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/244476?ContentTypeID=1Tue, 14 Apr 2020 13:51:46 GMT137ad170-7792-4731-bb38-c0d22fbe4515:53c29e0f-0c21-4286-bda1-b9d9c4e0b40bEdvin<p>Hello,</p> <p>NRF_DFU_APP_DATA_AREA_SIZE is set from DFU_APP_DATA_RESERVED, and is used in&nbsp;cache_too_small in&nbsp;nrf_dfu_cache_prepare.</p> <p>As you say, the reason it was not erased is that your application wasn&#39;t that large that it overwrote the FDS pages.&nbsp;</p> <p>You should really set&nbsp;DFU_APP_DATA_RESERVED according to the size of your FDS requirements to avoid corrupted data in your FDS pages. You should update the bootloader.</p> <p></p> <p>Best regards,</p> <p>Edvin</p><div style="clear:both;"></div>