How to define a 1MB continuous Flash memory area?

How to change the layout of 4MB Flash? My firmware package is probably over 1MB.
OTA1 planning is 1.5MB
OTA2 planning is 1.5MB
The remaining area is 1MB, customized for FlashDB database storage.

When I use Arduino IDE to program, there are roughly the following 4 areas:
Flash area 0: 0x08000000
Flash area 1: 0x08100000
Flash area 2: 0x08200000
Flash area 3: 0x08300000

I tried to modify the starting addresses of OTA1 and OTA2, but it always failed.

I found that every time the IDE burns and uploads, area 1 and area 3 are blank. There is firmware data for area 0 and area 2, and they are exactly the same? why is that? Did the IDE burn to area 0 and area 2 twice?

it is related with OTA strategy, try use area 1 or area 3 only. for example use 1, and 3 as backup.