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Before updating the tablet software, it's recommended that you back up the memory to ensure that no data is lost. It can also be useful to back up the device memory regularly to ensure that no data is lost in case of defects and crashes.
Back up the memory using iTunes, go to 1a.
Back up the memory using iCloud, go to 1b.
1a - Back up the memory using iTunes
Depending on your settings in iTunes, backup may start automatically.
1b - Back up the memory using iCloud
Log on to iCloud if you're asked to do so.