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- Archive object values - (primary archives) allows to archive implement archiving of values of D2000 system objects. Archiving can be either periodical or on value change.
- Calculate archived values by statistical function (statistical archives) - allows implement applying of a statistical function to a defined object of Historical value.
- Calculate archived values by defined statement (evaluated archives) - allows support defining a custom formula on top of existing objects of Historical value type. The formula is defined in the Statement tab. The results of the calculation are again values , that will be archived.
- Fill archive from the script (Value storage) - values can be written either from an ESL script or manually from the process D2000 HI.
Note: all types of Historical values (also primary, statistical, and evaluated) can be modified from an ESL script or manually from the process D2000 HI).
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The input field is enabled if the Publish values option is checked. It allows you to define an object, that will contains values of the historical value. When archiving a simple historical value, the target object must not be defined. However, it must be defined for one-column historical value, and for structured historical value - the size of the target object must be the same as the size of the object defined by the parameter Object to archive.
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- If it is not defined, the historical value is a simple one.
- The historical value is a one-column one if the parameter contains:
- column of a structured historical value (e.g. H.Struct[0]^ColName)
- one-column historical value (e.g. H.ColArchiv)
- column of an object of Structured variable type (e.g. SV.Struct[0]^ColName)
- The historical value is a structured one if the parameter contains:
- structured historical value
- an object of Structured variable type
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- Continuous - continuous (on the fly) calculation. Result values are calculated on the fly and they are automatically available (depending on the system load). A disadvantage of the method is a higher demand for computing power (especially for frequent changes of primary historical values that enter into the expression).
- On demand - the calculation is executed and the result is stored in the archive on demand. The demand can be generated by the CALCONDEMANDSTAT action or by the RECALC command ).
Note: historical value calculated "on-demand" should not have any depending historical values calculated continuously, because their results would be wrong. - On read - the calculation is executed as a result of a read request. An advantage of this method is that values are not stored in the database so they don't occupy any disk space. There is no possibility of re-calculation in case of writing delayed data into the archive. A disadvantage is the necessity to read source data and calculate it for each read request. This method should be used for objects whose values are rarely needed.
Note: historical value calculated "on-read" should not have any depending historical values calculated continuously or "on-demand", because the result could be wrong in some cases (due to delayed data) or the calculation could be ineffective (multiple calculations of a single "on-read" object if it is used by several other historical values).
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Archiving time (Months : Days : Hours). The parameter determines the archiving time depth. It is the minimal time period, during which the data will be stored in the on-line online archive. The older data are being erased from the archive.
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For periodical data archiving, it defines what time data with the value for the given period will be stored into in the archive. The time data can present either the beginning time - the "Period begin" option, or the end time of the interval (period) - the "Period end" option.
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- Continuous - continuous (on the fly) calculation. Result values are calculated on the fly and they are automatically available (depending on the system load). A disadvantage of the method is a higher demand for computing power (especially for frequent changes of primary historical values that enter into the expression).
- On demand - the calculation is executed and the result is stored in the archive on demand. The demand can be generated by the CALCONDEMANDSTAT action or by the RECALC command ).
Note: historical value calculated "on-demand" should not have any depending historical values calculated continuously, because their results would be wrong. - On read - the calculation is executed as a result of a read request. An advantage of this method is that values are not stored in the database so they don't occupy any disk space. There is no possibility of re-calculation in case of writing delayed data into the archive. A disadvantage is the necessity to read source data and calculate it for each read request. This method should be used for objects whose values are rarely needed.
Note: historical value calculated "on-read" should not have any depending historical values calculated continuously or "on-demand", because the result could be wrong in some cases (due to delayed data) or the calculation could be ineffective (multiple calculations of a single "on-read" object if it is used by several other historical values).
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The system allows archiving of significant changes in the values of the archived object. This method of archiving represents the definition of three sensitivity bands in which it is possible to enter different values of a significant change.
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