Re: Change PVA structure dynamically during IOC operation

["Kasemir, Kay via Tech-talk" <tech-talk at aps.anl.gov>]

> I need to change a PVA structure dynamically during IOC operation. Looking at pvxs::ioc::server, I do not see an update function that allows that. Does anyone know if this is possible?

I don't think that's possible.

If you check the protocol documentation, https://github.com/epics-base/pvAccessCPP/wiki/protocol, you'll find that the overall structure information is exchanged once when a client connects. From then on, only a compact bitmap that indicates what changed is sent, plus the modified values.

To change the structure, the protocol would have to send the complete new structure.

Arrays can change the number of elements, but the overall structure stays the same because the protocol was optimized for this.