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Trend - page of object PmTrend

Description:
Basic configuration of the trend group. By using the PmTrend object the PROMOTIC application becomes the trend server. In the trend server (one running PROMOTIC application) it is possible to define more trend groups (or PmTrend objects).
Configuration items basic:
Group ID identifierIdentifier of the trend group. It is the mandatory item. The trend group represents the PmTrend object and the designer must ensure that two groups haven't the same identifier. Then this identifier is used for example in the URL address of the Web trend component. If, for example, group1 is set, then the Internet URL address of this group data is http://computername/group1 (if the PmTrend object enables the data for the Internet in the page PmTrend > Web Server using the PmWeb object). In such case the computername is the name of the computer where the trend server is running, and group1 is the Web component identifier in the Web Server page (this name is identical with the name in this configurator).

Macro expression can be used for input (it is evaluated while the application is launching).

This is a system name and must not contain empty string, diacritics, spaces and the first character must not be a number.
Group user nameUser's name of the group (or the PmTrend object). This name is used for viewing as the user's identification of the group.

Macro expression can be used for input (it is evaluated while the application is launching).

Records number in memory cashNumber or records that are stored in the memory. If the data are stored on the disk (i.e. the Use the data on the disc configurator is checked), the data are stored on the disk and the assigned number into the memory as well in parallel. On processing actual client's queries the trend server needn't query the data from the disk because these actual data are available in the memory in parallel. By the definition of this constant it is necessary to realize that on high number of records in the memory (>1000) there is certain RAM memory-intensity of the computer.

For example if a higher number of variables is archived in all PmTrend objects together (for example let's have 1000 variables all together) and at all PmTrend objects the configurator Use the data on the disc has been set to 2000, the additional requirement about 1000*2000*8 = 16 000 000 Bytes = about 15 MB of the computing memory arises (the number 8 in the expression is the size of the Double data type).

Precision of time storage [s]Precision of time storage in seconds. Before the storage into the memory/disk, the time is rounded up to the specified precision. This entered precision must by supported even by the system for storing on the disk itself (if the data are stored even on the disk). The maximum possible precision depends on the type of the storage on disk:
Standard/local time storageStorage type of the time
Time is "local time" - In the daylight-saving season the time is saved as the "daylight-saving time", in the standard season as the "standard time". Thus the time is saved so as it has been get for example on calling the Run method.
Time is "standard time" - In the standard season the time is saved unchanged and in the daylight-saving season the time is decreased by 1 hour and thus it is always saved as the "standard time". This type ensures the correct functionality of the viewer in time of transition "standard time"/"daylight-saving time" and vice versa and thus it is recommended.
Read only (new records can't be written)If the Storage type setting is set to any saving method other than Database Access backups (obsolete), Database MS SQL server backups (obsolete) or Promotic binary file cyclic, then this setting can switch the object into the "Read only (new records can't be written)" mode (i.e. rading the data from existing files). In such case, the PmTrend object reads the data from PROMOTIC system databases, or from databases created by any other system. The database table from which the data have to be read this way, must include the time column configured as the Date and time data type. In this mode the object doesn't allow to write the data (by the methods Run, RunTime), but other functionality remains (displaying the data by the TrendsView viewer, statistics and evaluation of the data by the methods GetData, CreateFilter, saving the data into the file SaveToFile). Open methods makes dynamic connecting to requested table possible.

In this mode it is not needed to define the list of variables on the Data page (list of variables is read from the file as the list of columns of the database table). If the list of variables is defined on the Data page, it is synchronized with the list of columns from the database table.

See: PmTrend object in "Read only (new records can't be written)" mode.

Macro expression can be used for input (it is evaluated while the application is launching).

Automatic value saving after the launch is enabledIf checked, the automatic value saving after application launch is enabled. The PmTrend contains an internal timer (similar to the PmTimer object), allowing to save the selected values after defined time period. During each automatical saving (new record) the onAddRecord event is fired, the same ways as saving the values via the Run or RunTime methods. This event can be used for preparing the data to be saved.
Autosave period [s]The period in seconds. Always after this time perios is up, the Run method is called internally, which first calls the onAddRecord event and then saves all current values from the Data page.
Save variable changes onlyEnable optimized value saving. In this case the values (defined in Data page) are stored (into memory, on the disk) when calling the Run, RunTime method, only if the value has been changed since the last save and the difference is greater than the insensitivity range. The insensitivity range is a numeric value, defined separately for each variable, see Dead band. If at least one variable defined in the Data page of the PmTrend object does not fit its insensitivity range, then all variables defined in this page are saved.
Change evaluation methodVariable change evaluation method:
simple - by variable change - The variable change is evaluated as a difference between the new saved value and the value saved last time. If the new variable value is for example 35 and the last saved value is 34 and insensitivity range is 4, then the new value fits into insensitivity range (34-4/2,34+4/2)=(32,36) and the value is evaluated as unchanged.
optimized - by direction change - The value change is evaluated as the difference between the new saved value and the direction (slope=rise/run) of straight line connecting the values saved so far. In this case the insensitivity range is applied to the slope of the straight line connecting the value points.
If no change, save after [s]If the new values are repeatedly evaluated as unchanged (when calling Run, RunTime), then after the defined time interval (in seconds since last data save) the data save is processed during the next calling of Run, RunTime (the insensitivity is not evaluated).
See also:
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