Normally, the EFS folder is highly protected. Rooting and flashing ROMs normally do not touch this part of the device. Unfortunately, there is no such thing as a where everything goes according to plan in the real world. Sometimes, a process hits the EFS folder, or ends up corrupting the data within.
The EFS is also likely to be corrupted by users who like to unlock smartphones since it usually involves editing the data within the EFS folder. Once the data is corrupted, the only way to get it back to working order is to restore the data as is.
The loss of the EFS folder may cause your phone to no longer be recognized by your carrier or some of your radios may no longer work. This breaks the device as a whole no matter how many times you reinstall a ROM.
Even if you are not planning to modify the EFS folder itself, you can still accidentally corrupt that data. That is why even if the process of rooting and flashing ROMs does not require you to do so, it would be wise to back up the folder. This would be a case of being “better safe than sorry”.
Download miracle box https://docs.google.com/uc?id=0B66Lx4_xW...t=download
1. Go to developer option in your phone and enable usb debugging then connect your phone to pc
2. Open miracle box and navigate to Samsung tab then click scan to scan port which your phone is connected to and tick backup efs from the option
(Ensure to disconnect all other usb devices connected to your pc)
Then click start to start backing up EFS folder of your samsung
1. Also enable usb debugging
2. Goto Samsung tab and scan then select restore efs
3. Phone would reboot and you're all done