Knowledge Base

Using a different version of the VAREXP.DAT file, on stations that only exhibit client behavior, can significantly reduce the startup time. In the modified VAREXP.DAT file all variables of source type Equipment, OPC, IEC or BACnet should be set to Internal (I).

Please note that this solution may not be appropriate when the varexp.dat file is included in version control.

Technical background

Why is it faster to load an internal variable than an external variable on a client station?

When a variable is loaded, the source properties of the variable are loaded and a source object created independently of the function of the station,  producer or consumer. When the variable is subscribed, if the station produces the variable then the source object is unchanged,  if the station consumes the variable it is switched to external. The advantage of the implementation is that you can configure the source properties of variable  independently of the function of the station. The disadvantage is that many treatments are processed as the variable is loaded slowing the loading process.

PcVue 11.2 and later

In PcVue 11.2 and later the variable load process has been improved so that treatments for Equipment, OPC, IEC or BACnet are not loaded on client stations.