ClearSCADA

Protocol drivers within ClearSCADA behave as clients to the server, just like ViewX.  When an object in the database changes that the driver is interested in, it gets an interest update just like ViewX would, but only for configuration and not data changes.  This means a driver should be informed of a configuration change in relevant objects within a second or two. 

When the configuration of one of its objects changes, the driver looks to see if it already has a copy of it in its own internal database.  If it does not it will create it.  If it does exist in the driver, it compares the configuration of the new object with its copy.  If the driver considers the configuration change to be minor, it will slip the configuration changes into the copy within the driver and the driver will make use of the changes straight away.  If the changes are considered significant (such as changing an address), it will delete the existing object and create a new one in the driver based on the new configuration.  However this may not happen straight away.  Before the existing object can be deleted it must be in a safe state.  This means that any requests already actioned will be completed so there will be a variable amount of time before the new configuration becomes active.  However typically this will happen straight away.

An example of when it may not happen immediately would be making a change to a PSTN outstation that is significant, but it is currently in the middle of a PSTN call.  The driver will wait until the call is complete before applying the change.

Changes to communications timeouts are not considered significant so they will be applied straight away, effective from the next message sent after the change was made.