difference between shared variable and bound variable

Hello everybody,

I am new to OPC and have a question (at the moment) about OPC and LabVIEW.

I have to communicate with a third party PLC through an OPC-server delievered with the PLC. The OPC-Server ist installed on my PC.

In LabVIEW, I have configured an I/O-Server (OPC Client) and have created bound variables to the configured I/O-Server.

I want to use the Tag Reader/Writer VIs to read and write data to the PLC. When I access a bound variable for the first time in LabVIEW, it takes about one second before the bound variable is registered (?)

in LabVIEW. This is no problem with one or two variables, but I have to deal with at least 170 variables. So the first access will last about 166 seconds.

When I try the same with 'normal' shared variables (I used for this test the VIs from DSC Module -> Engine Control -> Variables & I/O Servers) the first access (with registering (?) ) will last only up to 10 seconds.

So what is the difference between the 'normal' shared variables and bound variables?

Thanks in aadvance for a answer

Heinrich