Pending update limit

The MaxUpdateQueue parameter sets the maximum number of events per consumer. The default is 50,000 pending updates per consumer. Similarly, the TotalUpdateQueue parameter sets the maximum events queued in the entire Update Manager database. The default number of maximum events is 1,000,000.

If either of these limits is reached, a message is sent to the PI message log. Another message is sent when the level goes back below 99 percent of the limit and queuing is resumed. Messages for consumers using less than 0.1 percent of the TotalUpdateQueue limit (100 for the default) are still queued even when the total limit is reached.

The default value is suitable for most systems, with the following exceptions:

• Increase the value on systems with:

  • Very large physical memory

  • High frequency of updates (normally snapshots)

  • Applications that might retrieve update limits slowly

• If a PINet node or PItoPI interface is connected to the Data Archive server, the default MaxUpdateQueue value is likely to be too small. Increase the value to at least the point count of the Data Archive server. This value ensures that all point updates requested by PINet can be queued if a system manager performs an edit operation on every point.