/dev/mmcblk1p1 has become full in beaglebone black industrial

/dev/mmcblk1p1 3.5G 2.3G 994M 71%

It was found that my mmcblk1p1 disk usage is increases day by day. I have running two processes continuously in mmcblk1p1 (/home/debian) folder.
Is that causes my mmcblk1p1 disk usage increment.
Or mmcblk1p1 is flash memory?, where processes or exes running in this “mmcblk1p1” causes any issues

Is the board connected to the internet?

and check which files are growing.

Yes, Is that causes any issues?

Actually I go for log rotation method
therefore Log files(/var/log/) does not increases now
also Files opened by firmware does not increases

One example is if you have UFW running and allow ssh, it will log every attempt. It is on by default and you need to turn logging off. If you allow 22 thru your gateway plan on every nefarious actor on the internet taking a try on your device…So, this is just a drop of water in a the ocean.

Many other issues regarding your device on the internet. All you can do is monitor what is going on and maybe write some code to look at what files are generating the issue.