Non-Historian data storage considerations

As a system is put into service, it is normal to maintain the Historian node to ensure enough space is available for continued data storage. This is a requirement for any historian. However, the Historian is not the only storage mechanism that is used in System Platform.

Nodes other than the Historian Node are capable of storing large amounts of information, so it is important to assess the impact of the following settings on data storage:

• Alarm Buffer Size: If the network connection to the alarm database is lost, the alarms will begin to be stored in a local buffer. This buffer is a direct reflection of the page file size. An average alarm record is 1400 bytes of data. If the buffer fills up, storage will stop. However, a 10 MB page file can store over 3500 alarms, so using the proper precaution can easily prevent an issue.

• Log Viewer Event Storage: By default, the Log Viewer event storage mechanism (which is installed on all computers) is set to use a maximum of 5 GB of storage. You can adjust this value. The Log Viewer event storage must be considered in the total disk space requirements.

• Store-and-Forward Deletion Threshold: The amount of free space that is reserved on the local HCAL store-and-forward disk. This reserved space is used for storing the historical data until the network connection is restored, if the network connection to the Historian is lost. The default circular deletion threshold is 100 MB. You should consider your requirements for this setting, and adjust it, if necessary, in the WinPlatform or the AppEngine object configuration.

When evaluating system configuration, it is worth spending a little time up front to consider disk space availability.