Agents
Agents provide a wide range of powerful capabilities. They can act as interfaces between subnets with different address spaces, support load balancing for backup jobs, and depending on the data type, eliminate the need for a separate editor license. More broadly, agents help reduce the processing load on the versiondog server by offloading upload and comparison tasks.
During the versiondog server installation routine, the agent setup is stored in the server archive. This setup supports the SmartUpdate process and can also be used to install agents on designated systems, such as engineering stations, HMIs, or industrial PCs.
When agents are installed on a target system, two new services are automatically configured: VDog UploadAgent and VDog CompareAgent. These services can perform the following tasks:
- Execute jobs that are configured in versiondog
- Create network transitions (e.g. when changing protocol from TCP/IP to Profibus)
- Backup HMIs, such as WinCC from Siemens
- Access the resources of the computer on which it was set up
- Use editors that are required to perform uploads and/or comparisons on a third-party computer
The HMI upload and compare agent
A variant of the agent is designed to back up HMI systems. The HMI upload and compare agent is able to back up the SCADA system WinCC from Siemens during runtime. This requires special capabilities, as the system is normally in operation (runtime) and therefore the files from the integrated databases are subject to constant access.
The reason for using such an agent is that the operator station does not have to be shut down in order to trigger a backup. Downtimes are therefore directly avoided.
The upload and compare agent
All automation devices supported by versiondog can also be backed up via the agent. An agent therefore has a similar range of functions to the regular server application. The advantage is that the agent relieves the main server by receiving and processing only those jobs from it that have been directly assigned to it. The result of an outsourced backup is then automatically forwarded to the main system and transferred. An agent supports all integration environments, which means that the most complex structures can be implemented. This variant is often used to operate a kind of scaling or load balancing.
The server now takes on a "delegation role". Upload jobs that are too much for it or for which it may not have a necessary editor license are transferred to "its" agents, who take over the operational work and communicate the results to it.
An upload and compare agent can also build bridges between networks whose participants speak different languages. As shown in the figure below, they are subject to different, mutually incompatible protocols (TCP/IP and Profibus). However, the agent can now also reach the Profibus devices and can transfer their uploads to the TCP/IP network in the direction of the versiondog server.
As an agent provides the functionality for uploads and comparisons, it is possible to separate these functionalities, so that one computer system performs the upload using the agent and another performs the comparison. In principle, the larger the customer and the larger the production environment under consideration, the more likely it is that networks are separated and that an agent offered will bring worthwhile benefits in at least one form.
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