To enable restricting and purging of scenario instances, set the enableScenarioRestrictionAndPurging property of the /atg/scenario/ScenarioManager component to true:

enableScenarioRestrictionAndPurging=true

The enableScenarioRestrictionAndPurging property is false by default. Setting this property to true enables you to specify the maximum number of instances of a scenario that can persist at a given time and how long an instance is available before it expires. In addition, you must set the enableScenarioPurgingJob property of the ScenarioManager to true on the server you want to run purging jobs on, as discussed in Configuring Scenario Instance Purging. Note that expired instances continue to count toward the maximum number of instances until they are purged.