If several business services (BS) change in one impact calculation, it loads the AlertHistory records for each BS. But if an alert appears in more then one business service, it will load it twice.
The impact job is responsible for calculating all the impact, including calculatong the dashboard (Event management > Dashboard), and the severities on the bs-map (drill down from a group). Disabling the job will keep the impact on dashboard as is, and not change according to new alerts.
Steps to Reproduce
Set impact calculation scheduled jobs.
For more information, see the product documentation topic Scheduled jobs installed with event management.
Note that Event Management - Impact Calculation repeatedly turns off and there are OOM issues when running impact calculation.
For a permanent fix, if you are able to upgrade, review the Fixed In field to determine the versions that have a permanent fix.
For a workaround if you cannot upgrade: Set the table cleanup sys_auto_flush for the em_alert_history table to two days instead of a week. Change the Age in seconds setting from 604,800 to 172,800. The Age can be decreased to 1 day (86400 seconds) if the out-of-memory issue still occurs.
Navigate to Table Cleanup.
Under System Maintenance, go to Table Cleanup, and click New.
Use the following settings:
Age in seconds: 172,800
Related Problem: PRB1057120