Urgent: File under a partition not retained at the time device restart

For flashing NK.bin image in my device i have created 2 partitions in my nand flash. Those are mounted like
a. /boot
b. /data
I have copied the NK.bin image to boot partition.
My Application Settings file is in data partition.
But every time i restarted the device, Settings file
within data partition automatically deleted.

Why the file is not retained within that partition?.

I need an urgent expert's solution.

Regards,
Nahid