Encyclopedia of Database Systems

2018 Edition
| Editors: Ling Liu, M. Tamer Özsu

Point-in-Time Copy

  • Kazuhisa FujimotoEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1339


PiT copy; Snapshot


A point-in-time copy is a copy of original data as it appeared at a point in time. In a conventional backup operation, users often create a PiT Copy, while an application is in quiescing, to make the PiT Copy a consistent copy of original data.

Key Points

There are two popular implementation techniques for creating PiT Copies inside a storage system: split mirror and copy on write.

Split mirror is a technique for replicating the original data at a point in time. In some implementations, a storage system replicates the original data, and when users create the PiT Copy, a storage system splits the replication. Copy on Write (CoW) is a technique for capturing data changes to storage and creating a PiT Copy after specifying the point in time. In some implementations, when users create the PiT Copy, a storage system creates its image with both the original data and the modified data.

Techniques for creating PiT Copies have a trade-off between occupied...

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Recommended Reading

  1. 1.
    Alain Azagury, et al. Point-in-time copy: yesterday, today, and tomorrow. In: Proceedings of the IEEE Symposium Conference on Mass Storage Systems and Technologies; 2002.Google Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Hitachi Ltd.TokyoJapan

Section editors and affiliations

  • Masaru Kitsuregawa
    • 1
  1. 1.Inst. of Industrial ScienceUniv. of TokyoTokyoJapan