When the SmartEvent Correlation Unit reads a log, it first checks if the log matches all defined Global Exclusions. Global Exclusions (defined on the Policy tab > Event Policy > Global Exclusions) direct SmartEvent to ignore logs that are not expected to contribute to an event.
If the log matches a Global Exclusion, it is discarded by the system. If not, the SmartEvent Correlation Unit starts to match it against each Event Definition.