How to
Editing the Maximum Transfer Interval Property of an Extended Trend Log
You edit the maximum transfer interval property to establish the time interval between two transfers.
You use an extended trend log to transfer records from a trend log. An extended trend log can be connected to a trend log or connected in a series to another extended trend log. Only one extended trend log can be connected to a trend log.
The extended trend log cannot log a variable.
Do not connect more than one extended trend log to a trend log or another extended trend log. If a trend log is connected to two or more extended trend logs, critical conflicts can occur.
The extended trend log is often saved on a higher server level with more storage capacity than the server of an ordinary trend log. This extra storage capacity enables the server to store more records before it overwrites old ones. The extended trend log can be viewed in a trend log list or a trend chart.
You can configure the extended trend log to transfer data several ways: Smart log, percentage, time interval, or force transfer.
Function | Explanation |
Smart log | Automatically updates the transfer rate with respect to the frequency of records, network speed, and the capacity of the servers that runs the trend log and the extended trend log. |
Threshold | Transfers records every time a set percentage threshold of records on the trend log is reached. |
Transfer at least every | Transfers records at a set time interval even though the threshold or Smart log condition is not reached. |
Force transfer | Executed by the user to manually force a transfer even though transfer threshold is not reached. |
When you edit a record in the extended trend log the changes do not affect the connected trend log. If you edit a record in the trend log, the changes are transferred to the extended trend log next time a transfer occurs. You can edit both the trend log and the corresponding record in the extended trend log, but in this way the edit is written twice in the extended trend log record in certain circumstances:
When the record in the extended trend log is manually updated
When the corresponding edit is transferred from the trend log to the extended trend log.
The trend log list or trend chart displays the last written value of an edited record.
Example 1: You edit a record in a trend log that is connected to an extended trend log. The extended trend log is updated with the edited record. After the transfer, you update the corresponding record in the extended trend log. The trend log list and trend chart connected to the extended trend log display the last value of the record, which in this case is the extended trend log edit.
Example 2: You edit a record in a trend log that is connected to an extended trend log. Before the extended trend log is updated with the edited record, you edit the corresponding record in the extended trend log. After a while the trend log transfers its edited record to the extended trend log. The trend log list and trend chart connected to the extended trend log display the edited trend log record value and not the edited extended trend log record value. In this case, the trend log list and trend chart display the last value that was written to the extended trend log, not the last edited value.
You can view all edits, automatically transferred or manually added, in the record history.
In WorkStation, in the System Tree pane, click the extended trend log whose maximum transfer interval you want to edit.
In the Extended Trend Log properties, in the Maximum transfer interval box, select the new value.
Click the Save button
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Configuring an Extended Trend Log
Extended Trend Log Properties
Extended Trend Logs