What is the main goal of Multiprocess ?

When you have a disk or memory I/O device, it does not matter what protocol you use. The protocol just determines what address format you use for the tags you create. Using OPC does not mean you are communicating with an OPC server. Since you have the device configured for Memory mode, all it means when you use OPC is that Citect doesn't care what addresses you use. This is not a hack--it is the recommended method for creating disk/memory/persisted devices. The generic protocol was the recommended method many years ago, before OPC had been invented. It only exists for backwards compatibility with old projects.

If you use disk mode or you enable persistence mode (which is the easier and more reliable way of having values saved to disk), then the memory values will be backed up to disk so Citect retains them when you restart the runtime. Still, it does not matter what protocol you used.

When you have a disk or memory I/O device, it does not matter what protocol you use. The protocol just determines what address format you use for the tags you create. Using OPC does not mean you are communicating with an OPC server. Since you have the device configured for Memory mode, all it means when you use OPC is that Citect doesn't care what addresses you use. This is not a hack--it is the recommended method for creating disk/memory/persisted devices. The generic protocol was the recommended method many years ago, before OPC had been invented. It only exists for backwards compatibility with old projects.

If you use disk mode or you enable persistence mode (which is the easier and more reliable way of having values saved to disk), then the memory values will be backed up to disk so Citect retains them when you restart the runtime. Still, it does not matter what protocol you used.

I am interested in the difference in protocol behavior when using the memory device which is in memory mode in the IO Device setting.

I currently using the Power SCADA Expert 8.2 which also citect base, and the NetworkTagDev for the EEhealth Tags by default is DISKXml after we tested within IEC61850N, If to use the OPC protocol, any foresee issues?