In BLU Vivo XL4 mobile, if the system partition gets corrupted, the mobile gets stuck in boot loop, i.e. the logo comes and gets stuck there. At this time, no recovery mode or fastboot works because the mobile is not able to read the boot script internally. At such a time, DA Auth File becomes necessary to use SP Flash Tool because this file takes the mobile into brom mode and gives specially signed access. When this access is obtained, you can clean not only the system partition but also the userdata, cache and metadata partitions and install fresh firmware. This process not only solves the boot loop problem but also improves the overall behavior of the mobile..
Many times, BLU Vivo XL4 mobiles experience auto restart issue, especially when an update fails or malware ROM is installed. This issue is caused by internal boot verification failure or corrupted security patch. SP Flash Tool does not detect the mobile without DA file because the mobile goes into strict verification mode. DA Auth File acts as a trusted bridge and paves the way for flashing by temporarily disabling the secure boot of the mobile. When you reinstall the correct firmware, not only the auto reboot issue goes away but the mobile takes on a new life.