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Status Declined
Categories Data Archive
Created by Guest
Created on Aug 20, 2022

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Reduce archive file size by eliminating unused record numbers

Background: On a Data Archive where many points have been deleted, there will be many unused record numbers. Since the size of an archive file is tied to the highest existing record number (for performance reasons), this can result in archive files that are much larger than necessary. Request: A method to eliminate unused record numbers, likely by modifying record numbers. As an example, three points with record numbers 1, 3, and 10 would turn into record numbers 1, 2, and 3.
  • ADMIN RESPONSE
    Aug 20, 2022
    Thank you very much for sharing your feedback on the PI Server. After further evaluation, we have decided to decline this item, as we are not planning on implementing it in the near future due to other high priority items across the PI System. Thank you for your feedback, and know that we are listening and reviewing every item that gets submitted!
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  • Guest
    Reply
    |     Aug 20, 2022
    Is there any way to estimate how much space is wasted per unused record number? That would help determine the importance of this idea.
  • Guest
    Reply
    |     Aug 20, 2022
    Each record number is approximately 1KB. So, if you have a PI Server that has 1mil tags and you delete 500 thousand, there will be approximately 500MB of each archive being used by empty record numbers.
  • Guest
    Reply
    |     Aug 20, 2022
    Maybe a tuning parameter can be added to specify the highest record number that will be used before the record numbers of deleted tags are reused.
  • Guest
    Reply
    |     Aug 20, 2022
    Hi Kenneth, this already happens automatically. It is only an issue if there are no plans to create many new tags, which would fill in the gaps in record numbers.
  • Guest
    Reply
    |     Aug 20, 2022
    I have a customer who split an archive collective into multiple collectives. One of the new collectives now has ~300,000 tags but over 5 million record numbers which is generating a lot of wasted space. Unfortunately they cannot reprocess the archives because the data archive does not honor digital state set changes (it applies the current digital state set to all previous entries). This has led to an enormous amount of wasted storage space during daily archive shifts.