+Turn OFF your PS Vita (Press Power Button for 10 seconds)
+Now press and hold “R” + Power + PS (PlayStation Button)
+Wait…
+Now you’re in Recovery Menu (Mode)

Recovery Menu Options

1. Restart System
This option boots your system as normal without changing any settings or files.

2. Rebuild Database
This can be a usefull feature if you have lost files on your system for no apparent reason. Try using this feature to see if it can restore those files. This will also rewrite corrupted files within the database, potentially eliminating future issues. This feature should not erase any of your saved data or settings.
Deletes messages, playlists, changes made on “Information” screens, trimming information for pictures in “Photo”, video thumbnails, video playback history and video resume information. This operation may take a long time depending on the type and number of data items.

3. Format the memory card
This will format the memorycard, effectively erasing all data currently on it.

4. Restore PS Vita System
This will restore your system to original including, formatting and erasing all of the data on internal flash and returning all system settings to default. This will not take your system back to a previous Firmware release. Use this option as a last resort, unless you have nothing on the console that you want or you want to erase everything on the console, do not use this option.

5. System Update
This can usefull if your system has become corrupted to the point you can not boot. This will allow the user to update their console with new firmware via
PS3
PC
PS Vita memorycard
Hope it is useful 
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