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Improved Reclamation Process through Selective Overwriting of Inactive Data on Sequential Access Media

IP.com Disclosure Number: IPCOM000029462D
Original Publication Date: 2004-Jun-29
Included in the Prior Art Database: 2004-Jun-29

Publishing Venue

IBM

Abstract

Sequential access media and devices, like tape, store data in a sequential order. In other words, the files are stored on the medium in the order they are written. This means when new files are written to a sequential access media, they are either written from the beginning or they are appended at the end of the last file. If a sequential medium is written from the beginning, it is considered a new medium, and all data files which reside on the tape from previous operations are overwritten. Appending data is possible from a certain position until the end of the medium is reached, and only the data that exist previous to the beginning of the write location are preserved. It is not possible to insert data in the middle of a sequential access medium. Eventually, some of these data files are no longer active and they become obsolete. To free up space on a media, previously, all active files from a piece of media were then migrated to a new piece of media, regardless of their position on the media, as the means of eliminating the obsolete files. The process of freeing up space on a media is also called reclamation. This publication offers a solution which minimizes the migration of active files onto new pieces of media.