OnOverflow Method (EventPipe object)

                    

 

This event is fired when the PI-SDK determines that the server update processing is in an overflow state tossing new events.  This comes about when the EventPipe fills (reaches its MaxCount of events) so new events are no longer retrieved from the server.  Eventually the server will stop saving events (rules vary depending on the type of server and configuration - consult server documentation for details) and start to throw events away.  When this happens and the PI-SDK requests new update events (this happens in a background thread, not the caller's thread) it will receive an error message indicating the overflow condition and in response the EventPipe will fire the OnOverflow event.  In this case the variant returned will be of type VT_NULL and the cause constant will be ocServerOverflow.

 

Syntax

Private Sub object_OnOverflow varItem, eCause

The OnOverflow method syntax has these parts:

Part

Description

object

An object expression that evaluates to a EventPipe object.

varItem

A variant containing the item that caused the overflow.  This event is not in the pipe.

eCause

A constant from the OverflowCauseConstants.  See Settings below.

 

Settings

The settings for eCause are:

Error

Description

ocMaxCountExceeded

The item if added to the event pipe would exceed its MaxCount property.

ocOutOfMemory

There is no memory to store the event.

ocServerOverflow The server update mechanism has overflowed and updates are being lost.

 

Remarks:

In implementations of the EventPipe prior to 1.3.2, when the MaxCount was exceeded, the client would continue to retrieve update events from the server but would toss them.  With PI-SDK 1.3.2 and beyond events are left on the server when they won't fit in the EventPipe.

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