zenon Disk Space Handling:
The zenon Service Engine, by default, stores process data on the hard disk. This is true for a standalone zenon project, as well as the zenon Service Engine server(s) in the zenon network topology. This data consists of Alarms, Events, Historian, Reports, Exports, etc. Although zenon uses highly efficient, native file formats by default - the amount of data recorded and accumulated by the zenon Service Engine can vary greatly depending on the project's configuration.
The purpose of this document is to provide an overview of data storage by the zenon Service Engine, and how it can be effectively managed to ensure optimal disk space utilization and performance, over a typical HMI/SCADA lifecycle of more than 10 years.
Why does the zenon Service Engine store data?
The zenon HMI/SCADA system not only handles real-time current values coming from the PLCs, IEDs, etc., but it is capable of maintaining records for historical reporting, analysis and compliance. The zenon Service Engine offers ready-to-use modules which are capable of reading from these historical files, and presenting the data in a variety of forms. For example, one such module is the Extended Trending. The zenon Historian can be configured to record measurement values for the last 3 months. These are saved onto the hard disk by zenon, and the Extended Trending module knows exactly how to read these files to present the user with a trend diagram in the Service Engine.
Where does zenon store the Service Engine data?
Service Engine folder: The zenon Service Engine Folder contains both the compiled zenon Service Engine Files and the zenon Service Engine Data. The Service Engine folder is commonly named with the zenon project name.
- Service Engine Files are the compiled project files created by the zenon Engineering Studio. The zenon Engineering Studio's Output Window will provide details about the compilation of the zenon project, but it is not necessary for you to become familiar with the different types of Service Engine files, and what they mean. The important thing to know is that your entire zenon project is compiled by the zenon Engineering Studio, into a set of Service Engine Files which the zenon Service Engine can interpret. The compiled zenon Service Engine Files are usually quite moderate in size and are generally not a concern in terms of hard disk usage. Once a zenon project is running live, the Service Engine Files do not grow or expand, unless the zenon system is expanded purposely by an engineer. The path where the Service Engine files exist on the target system is user-definable. However, the Service Engine files are consistently in a folder called RT e.g. C:\zenonRT\Project_SAS_1023\RT.
- Service Engine Data is the data that is created and managed by the zenon Service Engine. The Alarm Message List, Chronological Event List, and Historian are some modules that actually store Service Engine Data on the hard disk. Depending on the zenon project configuration, the Service Engine Data can grow and use more disk space as months and years of live zenon operation take place. The path where the Service Engine data exists on the target system is also user-configurable, but usually relative to the RT folder, in an own directory with the hostname of the PC e.g. C:\zenonRT\Project_SAS_1023\ServerA.
The following is some of the most common file types that the zenon Service Engine uses:
- .AML – The format written for a historical alarm file. To maintain historical alarm records, zenon by default, will create one alarm file per day automatically. The naming format for these files is the letter "A", followed by YYMMDD, example being A151109.AML. The size of the alarm files depend directly on how many alarms are configured within the zenon project, and the alarm occurrence frequency.
- .CEL – The format written for a historical event file. To maintain historical record of chronological events, zenon by default, will create one event file per day automatically. The naming format for these files is the letter "C", followed by YYMMDD, example being C150309.cel. The size of the event files also depend directly on how many events are configured within the zenon project, and the event occurrence frequency.
- .ARX – The default and native format written for an archive file saved by the historian module. The size of these files is dependent on multiple factors such as the historian recording type (cyclic, on change, event triggered), the amount of variables recorded, and how often there are changes. The naming format for these files is the short name of the archive, followed by a timestamp when the archive file was closed in the forrmat YYMMTThhmmss.