Substitution Value

Hi everyone,

I'm encountering an issue when trying to substitute an old value in a PI Point using the exact same timestamp. Instead of replacing the old value, PI System stores both values at the same timestamp.

For example, at timestamp 18/01/2025 16:00:00.000, two different values are recorded: 27.18221 and 13.31772. I expected the old value to be replaced, not stored alongside the new one.

My questions:

What are the common reasons why old values are not replaced even when the timestamp is exactly the same?
Are there any additional PI Point or interface/buffer configurations I should check?
How can I ensure that the data write operation truly performs a substitution rather than an append?

Top Replies

Rick_Davin_3.0 3 months ago +1

You have 2 options. One, you could delete the old value. This may not be feasible if you operate in an environment where all changes are to be audited. Two, when you go to write to substitute a value,…

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0 Gregor.Beck 3 months ago

Hello vsetia1 ,
there is different write modes like 'Insert' and 'Replace'. When using the Archive Editor add-in to PI SMT, the difference should be between changing the value of an existing record (Replace) and creating a new record (Insert). Replacing usually results into the "Substituted" value attribute being automatically set.
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0 Gregor.Beck 3 months ago

Hello vsetia1 ,
there is different write modes like 'Insert' and 'Replace'. When using the Archive Editor add-in to PI SMT, the difference should be between changing the value of an existing record (Replace) and creating a new record (Insert). Replacing usually results into the "Substituted" value attribute being automatically set.
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