integration Bootloader with central UART

[AP1]

1. HI currently i am using nrf52840 s140 sdk ver 17.1.0  i have integrted the secure boorloader /pca10056_ble sdk with central uart after merging i have faced run time error we need dfu ota for my main central uart app so thats why i am integrating to it i have tested secure bootloader it is working fine so i want to implement here 

2. second query is the secure bootloader ble only single app has taking 99.6 % of flash mem is it really taking that much mem

<error> app: Could not initalize DFU transport: 0x00000012
<info> app: Inside main
<info> nrf_dfu_settings: Backing up settings page to address 0xFE000.
<info> app: No firmware to activate.
<info> app: Boot validation failed. No valid app to boot.
<info> nrf_bootloader_wdt: WDT is not enabled
<info> app: Entering DFU mode.
<error> app: Could not initalize DFU transport: 0x00000012

[Sigurd]

Hi!

have integrted the secure boorloader /pca10056_ble sdk with central uart after merging

This is not the way to do it.

You keep the bootloader project and your application project as 2 separate projects. The code generated will reside in different parts of the flash, and you get 2 hex files(your app and the bootloader) that you flash to the device. 

If you are new to the bootloader see this guide:  Getting started with Nordic's Secure DFU bootloader, a step by step guide

PS: If this is a new project, then consider using nRF Connect SDK instead:  nRF Connect SDK and nRF5 SDK statement