Master Resetting your Device via the Settings Menu:

WARNING! Master resetting your device will result in deletion of your personal data that is saved on the gadget's internal storage (such as downloaded content, images, ringtones, contacts and apps). Remember that data stored on the SIM card or the SD card will not be deleted.

  1. If necessary, back up the data located on the internal memory
  2. Tap the "Applications" icon located on the home screen
  3. Tap "Settings"
  4. Tap "Back up & reset" under "Personal"
  5. Unmark the checkbox associated with "Automatic restore"
  6. Under "Personal Data", tap "Factory data reset"
  7. Press "Reset phone"
  8. Assuming that you have screen lock enabled, you will be asked for your password, PIN or pattern. Enter this information and press "Continue"
  9. Tap "Erase everything" to confirm

Hard Resetting:

Unfortunately, the Sony Xperia Z is not capable of performing a master reset via hardware key commands. Assuming that your device is frozen and you can't access the settings menu in order to reset your device, try doing the following:

  1. Press and hold the "Power" and "Volume Up" buttons
  2. Keep holding the aforementioned keys until your handsets vibrates three times (roughly 10 seconds)
  3. Release the keys
  4. Press the "Power" key again to turn on the device

Wiping the Cache Partition:

In case your handset is not working correctly and you're considering master resetting, then you might want to try and wipe the cache partition before doing so. Wiping the cache partition will not remove personal data stored on your handset's internal memory.

  1. While the device is powered on, press and hold the "Volume Up" and "Power" keys
  2. Wait for the display to shut down and for your handset to vibrate once
  3. Release the keys once that happened, then press the "Power" key to turn on your device

Booting in Safe Mode:

In case your smartphone won't completely boot after installing a third-party application, you can uninstall it by booting your device in safe mode. To do so:

  1. Press and hold the "Power" key
  2. Tap and hold "Power off"
  3. Press "OK". The device will now restart in safe mode
  4. While on the home screen, tap the "Applications" icon
  5. Tap "Settings"
  6. Under "Device" tap "Apps"
  7. Swipe left or right to access the "Downloaded" screen
  8. Select the application that is causing problems
  9. Tap "Uninstall" and confirm by pressing "OK"

To Turn Off Safe Mode:

  1. Press and hold the "Power" button
  2. Tap "Power off"
  3. After your device shuts down, hold the "Power" key again to restart it

See More: Sony Xperia Z: Master Reset, Wipe Cache Partition and Boot