Data Node Panel

The Data Node panel displays the basic information of the Historian Data Archivers (Primary Node plus Mirrors) currently available.

The Data Node panel displays data as described in the following table:


Field	Description
Connection	Indicates the status of the current connection. "Running" (Green) indicates that the Data Archiver is active. "Stopped" (Red) indicates that the Data Archiver is inactive. "Pause" indicates that the user has manually paused it.
Name	The logical name of the service.
IP	The IP address or the host name of the service.
Reason	Displays why the Data Node is not performing as expected. The reason is a warning message for the disk running out of space or memory. To view the details of the problem, move the mouse over the reason.
Details	Select this button to view the Data Node Detail Diagnostics.

Data Node Detail Diagnostics

The Data Node Detail diagnostics displays the data described in the following table. For each field, you can see the graphical representation of the values based on the time scales selected.

Note: The statistics displayed on this page are computed independently on various time scales and schedules. As a result, they may update at different times.

You can choose the time scales by selecting on the time options provided on the top right area of the page. To graphically view a particular parameter based on the timestamp, select the chart icon of the parameter. Select the data store available with the selected data node to view its disk free space and its statistics.

Table 1. Utilization Stats
Field	Description
Memory Utilization	Indicates how much server memory is being consumed.
Write Cache Hit Ratio	The hit ratio of the write cache in percent of total writes. It is a measure of how efficiently the system is collecting data and should typically range from 95 to 99.99%. If the data is changing rapidly over a wide range, however, the hit percentage drops significantly because current values differ from recently cached values. More regular sampling may increase the hit percentage. Out of order data also reduces the hit ratio.
Archive Compression	The current effect of archive data compression. If the value is zero, it indicates that archive compression is either ineffective or turned off. To increase the effect of data compression, increase the value of archive compression deadbands on individual tags in the Tag Maintenance page to activate compression. In computing the effect of archive compression, Historian counts internal system tags as well as data source tags. Therefore, when working with a very small number of tags and with compression disabled on data source tags, this field may indicate a value other than zero. If you use a realistic number of tags, however, system tags will constitute a very small percentage of total tags and will therefore not cause a significant error in computing the effect of archive compression on the total system.
Failed Writes	The number of samples that failed to be written. Since failed writes are a measure of system malfunctions or an indication of offline archive problems, the value shown in the display should be zero. If you observe a non-zero value, investigate the cause of the problem and take corrective action. The Historian also generates a message if a write fails. Note that the message only appears once per tag, for a succession of failed writes associated with that tag. For example, if the number displayed in this field is 20, but they all pertain to one Historian tag, you will only receive one message until the Historian tag is healthy again.
Out of Order	The number of samples within a series of timestamped data values normally transmitted in sequence have been received out of sequence since collector startup. This field applies to all collectors. Even though events are still stored, a steadily increasing number of out of order events indicates a problem with data transmission that you should investigate. For example, a steadily increasing number of out of order events when you are using the OPC Collector means that there is an out of order between the OPC Server and the OPC Collector. This may also cause an out of order between the OPC Collector and the data archiver but that is not what this statistic indicates.

Table 2. Process Rate
Field	Description
Read Queue Rate	Specifies the number of read requests processed per minute, that came into the archiver from all clients. A read request can return multiple data samples.
Write Queue Rate	Specifies the number of write requests processed per minute, that came into the archiver from all clients. A write request can contain multiple data samples.
Message Queue Rate	Specifies the number of messages processed per minute.

Table 3. Queue Size
Field	Description
Read Queue Size	Displays the total number of messages present in the Read queue.
Write Queue Size	Displays the total number of messages present in the Write queue.
Message Queue Size	Displays the total number of messages present in the Message queue.

Table 4. Disk Usage
Field	Description
Disk Free Space	The amount of disk space (in MB) left in the current archive.
Est. Days to Fill	The amount of time left before the archive is full, based on the current consumption rate. At that point, a new archive must be opened (could be automatic). To increase the days to full, you must reduce the Consumption Rate as noted above. To ensure that collection is not interrupted, you should make sure that the Automatically Create Archives option is enabled in the Data Store Maintenance page (the Global Options section). You may also want to enable Overwrite Old Archives if you have limited disk capacity. Enabling overwrite, however, means that some old data will be lost when new data overwrites the data in the oldest online archive. Use this feature only when necessary. The Estimated Days Until Full field is dynamically calculated by the server and becomes more accurate as an archive gets closer to completion. This number is only an estimate and will vary based on a number of factors, including the current compression effectiveness. The System sends messages notifying you at 5, 3, and 1 days until full.
Consumption Rate	The speed at which you are using up archive disk space. If the value is too high, you can reduce it by slowing the poll rate on selected tags or data points or by increasing the filtering on the data (widening the compression deadband to increase compression).