História stránky

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A text string describing the historical value. Maximum: 128 characters.
Possibility to use the Dictionary (to open click the CTRL+L).

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Technical units of the historical value. Maximum: 12 symbols. Possibility to use the Dictionary (to open click the CTRL+L).

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Values of the individual limits determine the state of the historical value according to its value. The relation value- limits gives give six possible states.

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Definition of a D2000 system object, values of which are to be archived. The object may be defined either by typing its name into the input edit field or by selecting it from the list of objects. To open the list of objects, click the button right from the input field.

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1. An object, the value of which is a simple type (Integer, Boolean, Real,...) - just one value is archived, therefore such archived object is called a simple historical value.
2. An item of an object of Structured variable type - there is also just one value archived, therefore such archived object is called a simple historical value, too.
3. A column of an object of Structured variable type (e.g. SV.Strct[0]^ColName) - there are archived all values of the column. Such an archived object is called a one-column historical value.
4. An entire object of Structured variable type (e.g. SV.Struct) - there are archived all values of the object. Such an archived object is called a structured historical value.

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• Periodical  - writing values into in the archive is are periodical. The archiving process stores the archive object value into the archive in defined time moments. Timestamp (the time of value) is not determined by the timestamp of the archived object value (e.g. an I/O tag), but by the time when the value is periodically written into the archive.
  
  Reading the values stored periodically by means of the D2000 system (ESL: GETARCHARR, GETARCHVAL, GETARCHROW, GETARCHCOL, GETARCHSTRUCT, D2000 ObjApi: GetArchivData, D2000 VBApi: VBApiGetArchData, D2000 WorkBook) follows the rule that the archive object's value out of time moments given by the period, is unknown (invalid). The result of the data reading is therefore given by the resampling and the begin (BT) and end (ET) time as follows:
  • resampling (step) = 0
    The reading results are all the values, the time of which belong into to the interval <BT, ET>.
  • resampling (step) <> 0
    The reading result is an array of values with timestamps contiguously:
    BT+0*step, BT+1*step, BT+2*step, ..., BT+N*step.
    The number of values is given by the end of the time interval (ET). The value of the array item is invalid if a record with the same timestamps does not exist in the archive database. If such a record exists, it is returned as a value of the array item. The above facts imply that when reading periodical data, it is necessary (advisable):
    • to adjust BT exactly to some of the object archiving moments, given by the period and time offset of the archiving.
    • resampling value (step) must be an integer multiple of the archiving period.
    • ET = BT + (N-1)*step, where N is an integer number: the number of values in the final selection.
    
    Note: The statistical archive, as far as reading is concerned, behaves as a periodical archive.

• Kotva
  sa_filter1 sa_filter1

  On value change - all the value changes of the archive object, which are not filtered out by the value filter, are stored in the archive.
  
  Reading of values stored by using a filter by means of the D2000 system (ESL:   GETARCHARR, GETARCHVAL, GETARCHROW, GETARCHCOL, GETARCHSTRUCT, D2000 ObjApi: GetArchivData, D2000 VBApi: VBApiGetArchData, D2000 WorkBook) follows the rule that the archive object's value at any time (t) is given by (equals to) the last historical value at or before the given time (t). The data reading result is therefore given by the resampling and the begin (BT) and end (ET) time as follows:
  • resampling (step) = 0
    The reading results are all the values, the time of which belongs to the interval <BT, ET> and one value before BT time, in case there is no value with a time exactly equal to BT time in the archive.
  • resampling (step) <> 0
    The reading result is an array of values with timestamps continuously:
    BT+0*step, BT+1*step, BT+2*step, ..., BT+N*step.
    The number of values is given by the end ET of the time interval. If a record with the same timestamps does not exist in the archive database, the value of the array item will be equal to the last value before the specific required (however, the timestamp will be set accordingly).

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• For a simple historical value - the object of the Historical value type you are configuring gets the last value (unless the parameter Historical value is defined).
• When archiving a one-column historical value - the last archived values of individual items are published in the relevant items of the column of a Structured variable type object defined by the Target object parameter.
• When archiving a structured historical value - the last archived values of individual items are published in the relevant items of a Structured variable type object defined by the Target object parameter.

Note: To ensure the correct functionality of the Publish values feature for a one-column historical value (structured HV) the number of rows (columns) of the structured variable defined in the Target object parameter must be the same as the number of rows (columns) of the object defined by the Historical value parameter.

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1. Create an object of Eval tag type, that adds together the values of the I/O tags and then archive archives it.
2. Create an object of Historical value type with the expression of „H.Flow1 + H.Flow2“.

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If checked, all invalid values of the objects defined in the expression will be replaced with the value of 0. The feature can be used to prevent the expression from getting invalid values. Only the values of input objects are replaced, and invalid values of intermediate data are not replaced. Values of inputs input objects are converted as follows:

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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 values calculated "on-demand" should not have any depending on historical values calculated continuously, because  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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For periodical data archiving, it defines what time data with the value for the given period will be stored 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 values calculated "on-demand" should not have any depending on historical values calculated continuously, because  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 value of the parameter Validation criteria defines the value percentage in the primary archive (used for the calculation of values stored into in the statistical archive) that has to be valid, in order to acquire a valid result. If there were fewer valid values than stated in the the Validity criteria, the result will be Weak_Value.

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• Average
• Sum
• Maximum
• Minimum
• Count
• EcoAvg
• Maximum in the time interval
• Minimum in the time interval
• Sum of positive values
• Sum of negative values
• Average of positive values
• Average of negative values
• Sample standard deviation

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