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Calculation methods
Definition of a methods method to calculate given expression - periodically or on value change. If the option On value change is option is selected, the expression will be recalculated when a value of at least one of the objects defined in the expression is changed.
Object An object of Historical value type defined in this way can be either simple or one-column historical value. If the object is a one-column historical value, the expression may also contain the references to other structured or one-column historical values with the row index of 0. During the calculation, the index is dynamically replaced by the current row number of the one-column historical value to recalculate. That allows to define defining the same expression for all column items.
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If the option Publish values is checked, than then the historical value will publish its last value:
- If the option is not checked, the parameter Structure size defines whether the historical value is is simple or one-column one.
If Structure size is not defined, the historical value is a simple one. If it is defined, the object is a one-column historical value - it is possible to define a column of a Structured variable type object, a column of a structured historical value, or a one-column historical value. The number of rows of the calculated one-column historical value is given by the number of rows of the objects defined in the parameter Structure size. - If the option is checked, the parameter Target column specifies whether the calculated historical value is simple or one-column.
If the Target column is not defined, the historical value will be a simple one that gets the last value.
If it is defined, the object will be a one-column historical value - it is possible to define a column of a Structured variable type object. So, the number of rows of the historical value is given by the number of rows of the target column.
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Definition of archive size - see the parameter the Publish values parameter. The parameter will appear, if the parameter be visible only if the Publish values parameter is not checked.
Target column
Definition of an object, that will contain values of the historical value - see the parameter the Publish values parameter. The parameter will appear, if the option will be visible only if the Publish values option is checked.
Kotva archiv_plneny_skriptom archiv_plneny_skriptom
FILL ARCHIVE FROM SCRIPT (VALUE STORAGE)
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Object An object of Historical value type filled from a script can be used as a storage of values which that are not generated by archiving the values of other D2000 system objectobjects, statistical calculation, or by other expression calculationcalculations. Values can be only filled from an ESL script or manually from the process the D2000 HI process.
Value storage can be simple, one-column, or structured one. This is given defined by the parameter Archive structure or Target structure (it depends on the parameter Publish values)
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If the option is checked, you must define a period and offset (the tab the Time parameters tab).
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Checking the option Publish values "renames" the parameter Archive structure to Target structure. The functionality of the parameter to define the structure of the archive is not changed, but however, it is not possible to define an object of Historical value type.
If the option the Publish values option is checked, the parameter Target structure defines whether the historical value is a simple or or structured one. If the Target structure is not defined, the historical value is a simple one and gets the last value. If it is defined, the historical value is a structured one and will fill publish the last value into the respective item of a defined structured variable.
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The parameter is enabled when the parameters Inserted values are periodical and Publish values are checked. If it is checked, the historical value will not publish its last value but the value that is valid according to the current time. (This feature supports storing data with future timestamps in an object of Historical value type - e.g. from a an ESL script , the feature allows to fill an object of Historical value type with values containing the future timestamps and - and then the object "plays" them these values in real-time).
Archive structure
The parameter appears when the the Publish values parameter Publish values is not checked.
- 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
- object of Structured variable type
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The parameter will appears if the parameter the Publish values parameter is checked. Allows It allows to define an object, that will contains contain values of the historical value - see the parameter the Publish values parameter. If it is not defined, the historical value itself will contain the values.
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In the top part of the tab, there is placed the an input edit filed is placed. It serves for entering the expression, that determines the value of the historical value. The expression can contains contain functions, constants, attributes - but objects of Historical value type only. The expression may also contain the contain extended syntax.
Objects
The button allows to select selecting an object of the D2000 system. Selected The selected object is to be inserted into the expression on the current cursor position.
Note: Expression can contain objects of Historical value type only.
Constants
The button allows to select selecting a constant. Clicking it open opens the dialog box containing the list of predefined constantconstants. Selected The selected constant is to will be inserted into the expression on the current cursor position.
Functions
The button allows to select selecting a function. Clicking it opens the "List of functions" dialog box. Selected The selected function is to be inserted into the expression on the current cursor position.
Attributes
The button allows to select allows selecting an attribute. Clicking it open opens the dialog box containing the list of attributes. Selected The selected attribute is to be inserted into the expression on the current cursor position.
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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 value. There are converted just values. Only the values of input objects are replaced, invalid values of intermediate data are not convertedreplaced. Values of inputs objects are converted as follows:
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The parameter can be defined for the archive method Filter. It allows to restrict restricting the number of evaluations of a given expression so that the expression will be evaluated once within a defined time. It is used especially in cases , when the values of the objects defined in the expression are often changed, and calculating the expression is not required immediately. It is used especially in cases , when the values of the objects defined in the expression are often changed, and calculating the expression is not required immediately.
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- Continuous - continuous (on the fly) calculation. Result values are calculated on the fly and they are automatically available (in dependence depending on the system load). A disadvantage of the method is a higher demand on the for computing power (especially for frequent changes of primary historical values).
- On demand - the calculation is executed and the result is stored to in the archive on demand. The demand can be generated by the the CALCONDEMANDSTAT action CALCONDEMANDSTAT or by the Tell RECALC Tell command RECALC ).
Note: historical value calculated "on demand" should not have any depending historical values calculated continuously, because the result 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 a the necessity to read source data and calculate it for each read demandrequest.
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 is defined, what time data with the value for the given period will be stored into the archive. The time data can present the begin beginning time - the "Period begin" option, or the end time of the interval (period) - the "Period end option" option.
Note: For archives filled from the script, this setting does not directly affect anything - the data has a time stamp timestamp with which it was stored from the script. It however affects the calculation of statistics and whether statistics are calculated from the value at the edge of the interval.
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Defining the conditions for the start and interruption of the archiving is provided by provides the mechanism of dynamical control of the object archiving dynamical control , depending on the values or states of others other objects in the system. Both conditions need not have to be defined. If not defined, the archiving will be started immediately after the start and initialisation initialization of the process Archive.
Start condition
Defining Definition of the condition causing the start archiving of the given historical value.
The object representing the archiving start condition may be defined by several ways:
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