The primary copy procedure ensures that the global objects are consistent at all times. This means that all copies of a particular global object contain the same value and any modification of a value is transmitted to all copies.
Primary and backup server
Only one automation station per site acts as the primary server for all global objects of this site. All other automation stations of this site are backup servers. A client may only modify the values of the global objects on the primary server. The primary server then updates the copies of the modified global objects on all backup servers. A backup server accepts the modifications to global objects only from its primary server but not from a client.
Xworks Plus (XWP) and all BACnet clients can only modify the data of global objects in the primary server.