OPC question - active communication

Dear,

I was reading something concerning OPC follows

the data transmission between the PA(control system level) and the PLC will be based on OPC access.

the PA will directly access the memory inside the PLC. there will be no active communication on PLC level for this data transmission

what do they mean by active communication, in this case, is it related to the access to the memory inside the PLC

thank you!

What PLC ?
What OPC server ?
What protocol ?
Who are "they" ?

Generally speaking, I think "they" mean that the data is read/written by the OPC directly, the data is not being sent/received by your CPU.

I think, that the only thing you have to do is allow for the OPC to connect to your CPU.

I might very well be wrong!

Quite possibly meaning that an OPC connected PLC, will not have direct read/write to the memory of another device on the PA network. I know on our DCS system, we utilize OPC for communicating to our third-party controllers to the HMIs. But our DCS controllers do not have the ability to directly(actively) communicate to those third party PLCs. We can do a trick within our system that looks for changes in a value, and then reads or writes to a tag within the DCS, but it does not have direct access.