PI point value handling for source write options

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Last UpdatedApr 13, 2026
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To avoid data loss, before you make PointType edits in your source PI Server, stop data collection in AVEVA PI System Connector 3 (PSC3). After all PointType edits are made, it is then safe to restart PSC3. This ensures I PointType edits are properly processed in the Connector and the source PI Server so that data is replicated as expected.

PSC3 replicates PI point values from the source PI System to the destination PI System. PI point values can be written to the source PI System using the following write options:

Insert
InsertNoCompression
Replace
NoReplace
ReplaceOnly
Remove

For all write options, the resulting disposition depends not only on whether a value exists at the specified timestamp, but also on whether the timestamp is equal to, earlier than, or later than the current snapshot.

Writes at the snapshot timestamp affect the snapshot, while writes earlier than the snapshot affect the archive. These cases are shown separately in the disposition tables even when other conditions appear the same.

Note: When PI point compression is enabled, PI compression rules determine whether a value is archived. When compression is disabled, values are always written to the archive

Insert

Insert writes values to the destination PI Data Archive based on the point’s compression setting and whether a value already exists at the timestamp.

PI Point Compressing	Value exists at timestamp	Incoming Timestamp vs. Snapshot Timestamp	Disposition Source PI Data Archive	Disposition on destination PI Data Archive
Yes	Yes	Timestamp = Snapshot	New value added as snapshot	Compressing rules apply. If archived on source, new value replicated.
No	Yes	Timestamp = Snapshot	New value added as snapshot	New value replicated. Previous snapshot value archived.
Yes	Yes	Timestamp < Snapshot (Out-of-Order)	New value inserted into archive	Not replicated or "Error: [-109] Value at This Time Already Exists
Yes	No	Timestamp < Snapshot (Out-of-Order)	New value inserted into archive	New value inserted into archive
No	Yes	Timestamp < Snapshot (Out-of-Order)	New value inserted into archive	Not replicated or "Error: [-109] Value at This Time Already Exists"
No	No	Timestamp < Snapshot (Out-of-Order)	New value inserted into archive	New value inserted into archive
Yes	No	Timestamp > Snapshot	New value added as snapshot	Compressing rules apply. If archived on source, new value replicated.
No	No	Timestamp > Snapshot	New value added as snapshot	New value replicated. Previous snapshot value archived

InsertNoCompression

InsertNoCompression behaves like Insert, except that compression is not applied when writing values.

PI Point Compressing	Value exists at timestamp	Incoming Timestamp vs. Snapshot Timestamp	Disposition Source PI Data Archive	Disposition on destination PI Data Archive
Yes	Yes	Timestamp = Snapshot	New value added as snapshot	Compressing rules apply. If archived on source, new value replicated.
No	Yes	Timestamp = Snapshot	New value added as snapshot	New value replicated. Previous snapshot value archived.
Yes	Yes	Timestamp < Snapshot (Out-of-Order)	New value inserted into archive	Not replicated or "Error: [-109] Value at This Time Already Exists"
Yes	No	Timestamp < Snapshot (Out-of-Order)	New value inserted into archive	New value inserted into archive
No	Yes	Timestamp < Snapshot (Out-of-Order)	New value inserted into archive	Not replicated or "Error: [-109] Value at This Time Already Exists"
No	No	Timestamp < Snapshot (Out-of-Order)	New value inserted into archive	New value inserted into archive
Yes	No	Timestamp > Snapshot	New value added as snapshot	Compressing rules apply. If archived on source, new value replicated
No	No	Timestamp > Snapshot	New value added as snapshot	New value replicated. Previous snapshot value archived.

Replace

Replace writes values to the destination PI Data Archive and replaces existing snapshot or archive values when applicable.

PI Point Compressing	Value exists at timestamp	Incoming Timestamp vs. Snapshot Timestamp	Disposition Source PI Data Archive	Disposition on destination PI Data Archive
Yes	Yes	Timestamp = Snapshot	Snapshot replaced with new value	Compressing rules apply. If archived on source, new value replicated.
No	Yes	Timestamp = Snapshot	Snapshot replaced with new value	New value replicated. Previous snapshot value archived.
Yes	Yes	Timestamp < Snapshot (Out-of-Order)	New value replaced archived value	Not replicated or "Error: [-109] Value at This Time Already Exists"
Yes	No	Timestamp < Snapshot (Out-of-Order)	New value inserted into archive	New value inserted into archive
No	Yes	Timestamp < Snapshot (Out-of-Order)	New value replaced archived value	Not replicated or "Error: [-109] Value at This Time Already Exists"
No	No	Timestamp < Snapshot (Out-of-Order)	New value inserted into archive	New value inserted into archive
Yes	No	Timestamp > Snapshot	New value added as snapshot	Compressing rules apply. If archived on source, new value replicated
No	No	Timestamp > Snapshot	New value added as snapshot	New value replicated. Previous snapshot value archived.

NoReplace

NoReplace writes values only when no value already exists at the specified timestamp.

PI Point Compressing	Value exists at timestamp	Incoming Timestamp vs. Snapshot Timestamp	Disposition Source PI Data Archive	Disposition on destination PI Data Archive
Yes	Yes	Timestamp = Snapshot	New value added as snapshot	Compressing rules apply. If archived on source, new value replicated.
No	Yes	Timestamp = Snapshot	New value added as snapshot	New value replicated. Previous snapshot value archived.
Yes	Yes	Timestamp < Snapshot (Out-of-Order)	New value ignored	New value not replicated.
Yes	No	Timestamp < Snapshot (Out-of-Order)	New value inserted into archive	New value inserted into archive
No	Yes	Timestamp < Snapshot (Out-of-Order)	New value ignored	New value not replicated.
No	No	Timestamp < Snapshot (Out-of-Order)	New value inserted into archive	New value inserted into archive
Yes	No	Timestamp > Snapshot	New value added as snapshot	Compressing rules apply. If archived on source, new value replicated
No	No	Timestamp > Snapshot	New value added as snapshot	New value replicated. Previous snapshot value archived.

ReplaceOnly

ReplaceOnly replaces existing values but does not insert new ones when no value exists.

PI Point Compressing	Value exists at timestamp	Incoming Timestamp vs. Snapshot Timestamp	Disposition Source PI Data Archive	Disposition on destination PI Data Archive
Yes	Yes	Timestamp = Snapshot	Snapshot replaced with new value	Compressing rules apply. If archived on source, new value replicated.
No	Yes	Timestamp = Snapshot	Snapshot replaced with new value	New value replicated. Previous snapshot value archived.
Yes	Yes	Timestamp < Snapshot (Out-of-Order)	New value replaced archived value	Not replicated or "Error: [-109] Value at This Time Already Exists".
Yes	No	Timestamp < Snapshot (Out-of-Order)	New value ignored	New value inserted into archive
No	Yes	Timestamp < Snapshot (Out-of-Order)	New value replaced archived value	New value inserted into archive.
No	No	Timestamp < Snapshot (Out-of-Order)	New value ignored	New value not replicated.
Yes	No	Timestamp > Snapshot	New value ignored	New value not replicated.
No	No	Timestamp > Snapshot	New value ignored	New value not replicated..

Remove

Remove removes values when possible; otherwise, the write is ignored.

PI Point Compressing	Value exists at timestamp	Incoming Timestamp vs. Snapshot Timestamp	Disposition Source PI Data Archive	Disposition on destination PI Data Archive
Yes	Yes	Timestamp = Snapshot	New value ignored	New value not replicated.
No	Yes	Timestamp = Snapshot	New value ignored	New value not replicated.
Yes	Yes	Timestamp < Snapshot (Out-of-Order)	Value removed from archive	Value not removed from archive.
Yes	No	Timestamp < Snapshot (Out-of-Order)	New value ignored	New value not replicated
No	Yes	Timestamp < Snapshot (Out-of-Order)	Value removed from archive	Value not removed from archive.
No	No	Timestamp < Snapshot (Out-of-Order)	New value ignored	New value not replicated.
Yes	No	Timestamp > Snapshot	New value ignored	New value not replicated.
No	No	Timestamp > Snapshot	New value ignored	New value not replicated.

PI System Connector 3