Data recovery

process of salvaging inaccessible data from corrupted or damaged secondary storage

error condition in information systems in which information is destroyed by failures or neglect in storage, transmission, or processing

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Undeletion is a feature for restoring computer files which have been removed from a file system by file deletion. Deleted data can be recovered on many file systems, but not all file systems provide an undeletion feature. Recovering data without an undeletion facility is usually called data recovery, rather than undeletion. Undeletion can both help prevent users from accidentally losing data, or can pose a computer security risk, since users may not be aware that deleted files remain accessible.