Agents
The agent is extremely functional. It can be used either as an interface between differently addressed subnets, as support for load distribution in the backup jobs to be performed or, for some data types, so as to avoid the otherwise necessary purchase of an editor license. In general, the agent can also be used to relieve the versiondog server by outsourcing the actual upload and comparison to an agent.
During the installation routine, the agent is also stored in the server archive and can be set up from there at the locations intended for use (for example, on an engineering station, an HMI, an industrial PC, etc.) Two new services are set up on the target system, which can perform the following tasks:
- Execute jobs that are configured in versiondog
- Creation of network transitions (for example, during a protocol change from TCP/IP to Profibus)
- Backup of HMIs, such as WinCC from Siemens
- Access to the resources of the computer on which the HMI was set up
- Use of editors that are needed to perform uploads and/or comparisons on a foreign computer
versiondog HMI Upload & Compare Agents
One variant of the agent is intended for the backup of HMI systems. The HMI Backup and Compare agent is capable of backing up the SCADA system WinCC by Siemens during operation. Special skills are required for this, since the system is normally in operation (runtime) and the files from the included databases are therefore subject to constant access.
The customer’s motivation for using such an agent is that they do not have to shut down their operator station in order to launch a backup. Stoppages are therefore directly avoided.
The versiondog Upload & Compare Agent
All automation devices supported by versiondog can be backed up via the agent. It possesses the same range of functions as the regular server application. The advantage is that the agent removes the load from the main server and that it only receives and processes tasks that have been sent directly by the main server. The result of an outsourced backup is then automatically passed on and taken over by the main system. An agent supports all integration environments and therefore handles the most complex structures and simplifies them. This method is often used to conduct some kind of scaling or load balancing.
The server assumes (if viewed as a person) the role of delegator. Upload processes which may prove too much for it to handle or for which the server does not have the required editor license can be delegated to “its†agents. These then carry out the necessary operations and communicate the results back to it.
A versiondog Upload and Compare agent can build bridges between networks whose participants speak different languages. As depicted in the figure below, they are subject to different protocols that are not compatible with one another (TCP/IP and PROFIBUS). By using the agent you can now also reach the PROFIBUS devices and carry out uploads to the TCP / IP network directed towards the versiondog server.
As an agent provides the functionality for uploads and comparisons, it is possible to separate these functions so that one computer system uses the agent to perform the upload and another carries out the comparison. In principle, the larger the customer and the larger the production environment, the more likely it is that networks are separated and that an agent offered will provide worthwhile benefits in at least one form.