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Trend - tab of the PmaTrendGroup object

Description:
Basic settings of group of trends.

By using the PmaTrendGroup object the PROMOTIC application becomes a trend server. In the trend server (running PROMOTIC application) it can be defined multiple trend groups (or PmaTrendGroup objects).

Configuration items basic:
Group ID identifierIdentifier of the trend group. It is a mandatory item. The trend group represents the PmaTrendGroup object and the designer must ensure that two groups do not use the same identifier. This identifier is used for example for addressing a variable in trend viewer. If, for example, group1 is set, then the internet URL address of this group data may be http://computername/group1 (if the PmaTrendGroup object enables the data for the Internet on the "PmaTrendGroup > Web server" tab by means of the PmaWeb object). In this case the computername is the name of the computer where the trend server is running, and group1 is the Web component identifier on the "Web server" tab (this name is identical with the name in this configurator).

Macro expression can be used for input (it is evaluated after starting the application).

This is a system name, so it must contain only alphanumeric and must not contain any diacritics, empty string, spaces and the first character must not be a number.
User defined name of the groupUser defined name of the group (or the PmaTrendGroup object). This name is used for displaying as user identification of the group.

Macro expression can be used for input (it is evaluated after starting the application).

Number of records in memory cashThe number of records that are stored in memory. If the data is to be stored to disk (i.e. the "Use the data on the disk" configurator is checked), then the data is stored to disk and the defined number of records also into memory simultaneously. When client queries are being processed the trend server does not have to load the data from the disk but it can use the current data that is also available in the memory. When setting this constant it is necessary to understand that a high number of records in the memory (>1000) may cause higher intensity of RAM memory usage.

For example if a higher number of variables is being archived by all PmaTrendGroup objects together (for example 1000 variables in total) and for all PmaTrendGroup objects the "Use the data on the disk" configurator has been set to 2000, then it causes additional requirement of about 1000*2000*8 = 16 000 000 bytes of RAM = approx. 15 MB of the RAM arises (the number 8 in the expression is the size of the Double type).

Timestamp accuracy [s]Timestamp accuracy in seconds. Before the timestamp is stored in the memory/to disk, the time is rounded up to the specified accuracy. This defined accuracy must by supported by the storage system disk itself (if the data is stored also to disk). The maximum possible accuracy depends on the type of storage on the disk:
Standard/local time storageTime storage type
Time is "local time" - During the daylight-saving season the time is saved as the "daylight-saving time", in the standard seasons as "standard time". The time is saved as it has been detected for example by calling the Run method.
Time is "standard time" - In the winter season the time is saved unchanged and in the daylight-saving season the time value is decreased by 1 hour and thus it is always saved as "standard time". This approach ensures correct functionality of the viewer in time of transition "standard time"/"daylight-saving time" and vice versa and therefore it is recommended.
Read only (new records cannot be written)If the "Storage type" configurator 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 be used to switch the object into the "Read only (new records cannot be written)" mode (i.e. reading data from existing files). In this case, the PmaTrendGroup object reads the data from databases created by the PROMOTIC system, or even from databases created by other systems. The database table from which the data are to be read must include the timestamp column configured as the Date and time data type. In this mode the object does not allow writing any data (by Run, RunTime methods), but other functionality remains unchanged (displaying the data by the PmgTrendViewer viewer, statistics and evaluation of the data by GetData, CreateFilter methods, saving the data into the file by SaveToFile). The Open method allows dynamic connecting to requested table.

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

See: The PmaTrendGroup object in "Read only (new records cannot be written)" mode.

Macro expression can be used for input (it is evaluated after starting the application).

Automatic saving after launch is enabledIf checked, then the automatic value saving after starting the application is enabled. The PmaTrendGroup object contains an internal timer (similar to the PmaTimer object), allowing to save the selected values after defined time period. During each automatic saving (new record) the onAddRecord event is triggered, the same way as during saving the values via the Run or RunTime methods. This event can be used for preparing the data to be saved.
Autosave period [s]Autosave period in seconds. Each time this period passes the Run method is called internally, then the onAddRecord event is triggered and then saves all current values on the "Data" tab.
Enable saving of variables on changeEnable/disable optimized value saving. In this case the values (defined on the "Data" tab) are stored (into memory, to 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 number, defined separately for each variable, see Dead band. If at least one variable defined on the "Data" tab of the PmaTrendGroup object does not fit its insensitivity range, then all variables defined in this tab 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 variable is evaluated as unchanged.
optimized - by direction change - The value change is evaluated as the difference between the new saved value and the direction (change in Y coordinate / change in X coordinate) 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, then 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 is saved during the next calling of Run, RunTime (the insensitivity is not evaluated).
See also:
PROMOTIC 9.0.10 SCADA system documentation - MICROSYS, spol. s r.o.

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