In the simplest process control system based on TeslaSCADA, every device (computer or mobile) is, in fact, a server, since it reads and writes tag values from/to devices, works with a database, etc.
The advantage of this architecture is that there is no need to use some intermediate device for the server. All connections are made directly to industrial devices and servers. A PC or mobile device can be used as an HMI.
The disadvantages of such a system are that with a large number of devices (PCs and mobiles) with TeslaSCADA, there is a load on the controller, the exchange of data when communicating with the controllers is via an unencrypted channel, and all the necessary calculations in scripts are carried out on each device.