PVSS00valarch - PARAM/WARNING - Attempt to write value before already existing one

Enclosed you'll find the explanation for a log-message which can during runtime of the project. The log-message is written to the PVSS_II.log-file.


PVSS00valarch(6), 2012.08.13 11:43:55.975, PARAM,WARNING, 51, Parameter incorrect, ArchivSet, sequentialWriteObject, Can't write value (ErrNum=7), ErrorDP: DpId = 25918, elementId = 94, Attempt to write value before already existing one
Archiving was stopped at Jän 01 2012 - 00:00:00.000, time of new value = Okt 31 2011 - 01:00:00.000
SetNum:50, previousIdx:1; valChanged:00d4


Log-message with symbolic names:

PVSS00valarch(6), <TIMESTAMP>, PARAM,WARNING, 51, Parameter incorrect, ArchivSet, sequentialWriteObject, Can't write value (ErrNum=7), ErrorDP: DpId = <DPE-ID>, Attempt to write value before already existing one
Archiving was stopped at <archive time-information>, time of new value = <timestamp of valuechange>
SetNum:<setfilenumber>, previousIdx:1; valChanged:00d4


This log-message describes that saving a value at the archive was not possible. The given <DPE-ID> information can be converted into a DPE-name using the CTRL-function dpGetName().

It occurs only in very special circumstances when using dp-elements with deactivated last-value-storage and dpSetTimed(). The last-value-storage can be activated/deactivated at the _original-config.

Enclosed you’ll find a description when the log-message will be written:
-- dp-element with deactivated last-value-storage, the stored time for the last value in the database is old (the time when the last-value-storage was deactivated)
-- at this dp-element an _archive-config is added for the value-archive
-- the _original.._value for the dp-element is set with the current time (e.g. 2012.09.18 12:00), this value will be saved at the archive
-- stopping the complete project
-- restarting the project
-- now the _original.._value for the dp-element is set with a time younger than 2012.09.18 12:00, e.g. 2012.09.18 11:00
This dpSetTimed() is possible without a correction of the timestamp by the event-manager because the timestamp for the last-value is old due to the fact that the last-value-storage is deactivated.
-- now the value-archive log-message occurs and the value which was set is lost

If the _original.._value for the dp-element is set with the current time or a time newer than the last value stored at the archive (e.g. newer than 2012.09.18 12:00) after restarting the project everything is OK and the value is saved at the archive.

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