WinCC OA-drivers - SYS/SEVERE - Driver output queue to EV manager exceeded (size 10000), starting overwriting of Values with same DPID

Enclosed you'll find the explanation for a log-message which can occur during runtime or when starting a driver. The log-message is written to the PVSS_II.log-file.

PVSS00<driver> (2), 2011.07.28 10:27:39.930, SYS, SEVERE, 145, Driver output queue to EV manager exceeded (size 10000), starting overwriting of Values with same DPID
PVSS00<driver> (2), 2011.07.28 10:27:44.274, SYS, INFO, 147, Driver overflow queue empty. Overwriting of Values with same DPID finished.

Log-message with symbolic names:

PVSS00<driver> (2), <TIMESTAMP>, SYS, SEVERE, 145, Driver output queue to EV manager exceeded (size <queuelimit>), starting overwriting of Values with same DPID
PVSS00<driver> (2), <TIMESTAMP>, SYS, INFO, 147, Driver overflow queue empty. Overwriting of Values with same DPID finished.

This log-message describes that the limit <queuelimit> for the message-queue in send-direction (driver --> event-manager) was exceeded. The second message appears when the queue size is below the defined limit.
The current limit is defined with the config-entry maxOutputQueueSize for the driver.
If the limit is reached the stability function “Overlad regulation for drivers” is activated at the driver.

When the overload situation is detected the dp-element _DriverX(_2).OV is set with the value "true" (X has to be substituted with the driver number, in case of a redundant system the driver connected to server 2 is using the datapoint with _2 postfix).

For further details please have a look at the PVSS/WinCC OA online help and search for the keywords “Error tolerance” and “stability”.

Most of the time it occurs during startup of the driver or when a general query is made, especially for drivers where a lot of addresses are configured. When you have made changes to the address-configuration please start a manual GQ to see if the log-message occurs.