Program Section .non_init what is it?

[Blastka]

Hello. Could you explain about file flash_placement.xml. 

<!DOCTYPE Linker_Placement_File>
<Root name="Flash Section Placement">
<MemorySegment name="FLASH" start="$(FLASH_PH_START)" size="$(FLASH_PH_SIZE)">
<ProgramSection alignment="0x100" load="Yes" name=".vectors" start="$(FLASH_START)" />
<ProgramSection alignment="4" load="Yes" name=".init" />
<ProgramSection alignment="4" load="Yes" name=".init_rodata" />
<ProgramSection alignment="4" load="Yes" name=".text" />
<ProgramSection alignment="4" keep="Yes" load="Yes" name=".log_const_data" inputsections="*(SORT(.log_const_data*))" address_symbol="__start_log_const_data" end_symbol="__stop_log_const_data" />
<ProgramSection alignment="4" keep="Yes" load="Yes" name=".nrf_balloc" inputsections="*(.nrf_balloc*)" address_symbol="__start_nrf_balloc" end_symbol="__stop_nrf_balloc" />
<ProgramSection alignment="4" keep="Yes" load="Yes" name=".nrf_queue" inputsections="*(.nrf_queue*)" address_symbol="__start_nrf_queue" end_symbol="__stop_nrf_queue" />
<ProgramSection alignment="4" keep="Yes" load="Yes" name=".pwr_mgmt_data" inputsections="*(SORT(.pwr_mgmt_data*))" address_symbol="__start_pwr_mgmt_data" end_symbol="__stop_pwr_mgmt_data" />
<ProgramSection alignment="4" keep="Yes" load="Yes" name=".crypto_data" inputsections="*(SORT(.crypto_data*))" address_symbol="__start_crypto_data" end_symbol="__stop_crypto_data" />
<ProgramSection alignment="4" keep="Yes" load="Yes" name=".cli_command" inputsections="*(.cli_command*)" address_symbol="__start_cli_command" end_symbol="__stop_cli_command" />
<ProgramSection alignment="4" keep="Yes" load="No" name=".nrf_sections" address_symbol="__start_nrf_sections" />
<ProgramSection alignment="4" keep="Yes" load="Yes" name=".log_dynamic_data" inputsections="*(SORT(.log_dynamic_data*))" runin=".log_dynamic_data_run"/>
<ProgramSection alignment="4" keep="Yes" load="Yes" name=".fs_data" inputsections="*(.fs_data*)" runin=".fs_data_run"/>
<ProgramSection alignment="4" keep="Yes" load="Yes" name=".cli_sorted_cmd_ptrs" inputsections="*(.cli_sorted_cmd_ptrs*)" runin=".cli_sorted_cmd_ptrs_run"/>
<ProgramSection alignment="4" load="Yes" name=".dtors" />
<ProgramSection alignment="4" load="Yes" name=".ctors" />
<ProgramSection alignment="4" load="Yes" name=".rodata" />
<ProgramSection alignment="4" load="Yes" name=".ARM.exidx" address_symbol="__exidx_start" end_symbol="__exidx_end" />
<ProgramSection alignment="4" load="Yes" runin=".fast_run" name=".fast" />
<ProgramSection alignment="4" load="Yes" runin=".data_run" name=".data" />
<ProgramSection alignment="4" load="Yes" runin=".tdata_run" name=".tdata" />
</MemorySegment>
<MemorySegment name="RAM" start="$(RAM_PH_START)" size="$(RAM_PH_SIZE)">
<ProgramSection alignment="0x100" load="No" name=".vectors_ram" start="$(RAM_START)" address_symbol="__app_ram_start__"/>
<ProgramSection alignment="4" keep="Yes" load="No" name=".nrf_sections_run" address_symbol="__start_nrf_sections_run" />
<ProgramSection alignment="4" keep="Yes" load="No" name=".log_dynamic_data_run" address_symbol="__start_log_dynamic_data" end_symbol="__stop_log_dynamic_data" />
<ProgramSection alignment="4" keep="Yes" load="No" name=".fs_data_run" address_symbol="__start_fs_data" end_symbol="__stop_fs_data" />
<ProgramSection alignment="4" keep="Yes" load="No" name=".cli_sorted_cmd_ptrs_run" address_symbol="__start_cli_sorted_cmd_ptrs" end_symbol="__stop_cli_sorted_cmd_ptrs" />
<ProgramSection alignment="4" keep="Yes" load="No" name=".nrf_sections_run_end" address_symbol="__end_nrf_sections_run" />
<ProgramSection alignment="4" keep="Yes" load="No" name=".retained_section" address_symbol="__start_retained_section" end_symbol="__stop__retained_section" size="8" />
<ProgramSection alignment="4" load="No" name=".fast_run" />
<ProgramSection alignment="4" load="No" name=".data_run" />
<ProgramSection alignment="4" load="No" name=".tdata_run" />
<ProgramSection alignment="4" load="No" name=".bss" />
<ProgramSection alignment="4" load="No" name=".tbss" />
<ProgramSection alignment="4" load="No" name=".non_init" />
<ProgramSection alignment="4" size="__HEAPSIZE__" load="No" name=".heap" />
<ProgramSection alignment="8" size="__STACKSIZE__" load="No" place_from_segment_end="Yes" name=".stack" address_symbol="__StackLimit" end_symbol="__StackTop"/>
<ProgramSection alignment="8" size="__STACKSIZE_PROCESS__" load="No" name=".stack_process" />
</MemorySegment>
</Root>

https://www.segger.com/downloads/embedded-studio/EmbeddedStudio_Manual page 207 Program sections. Some sections are not described. I'm currently interested section .non_inint. I use it to store variables after system OFF. 
https://devzone.nordicsemi.com/f/nordic-q-a/34395/status-of-sram-during-an-over-the-air-update/132658#132658 from here I took this method.

How does it work, why are there 3 more sections after it?

<ProgramSection alignment="4" load="No" name=".non_init" /> ????
<ProgramSection alignment="4" size="__HEAPSIZE__" load="No" name=".heap" />
<ProgramSection alignment="8" size="__STACKSIZE__" load="No" place_from_segment_end="Yes" name=".stack" address_symbol="__StackLimit" end_symbol="__StackTop"/>
<ProgramSection alignment="8" size="__STACKSIZE_PROCESS__" load="No" name=".stack_process" />
</MemorySegment>
</Root>

[Sigurd]

How does it work, why are there 3 more sections after it?

Typically, variables in RAM gets zero initialized during the reset sequence. If they are placed in the .non_init section they will not get zero initialized. You might find this post useful.

The placement of the .heap, .stack and .stack_process afterwards are not directly related to the .non_init section. 

[Blastka]

как сделать его равным 0 при программировании?
uint32_t value_in_character_timeshtamp _ _ атрибут__((раздел(".non_init")) = 0;

= 0 не работает

[Sigurd]

Only uninitialized variables can be placed in the .noinit section.

[Blastka]

I am interested in how this section appeared. This is not in the documentation. Can you give up the theory?