In JIRA, you can easily change the settings for the Quartz scheduler by editing the file: <JIRA_INSTALL>/atlassian-jira/WEB-INF/classes/quartz.properties

In Confluence it is not possible. The file does not exist and settings are not picked up when it is manually created.

This can be useful for cases with more than 10 external user directories, where all the scheduler threads may be taken and other scheduled task will be discarded after the misfire threshold (60 seconds).