Workaround
Cleanup or Delete the alert history for your alerts:
1. Open up the Change Auditor client as an administrator.
2. In 'Searches' tab click locate and select the search that your alert is based on.
3. Right-click on it and then navigate to Alert menu and select 'Delete History' option.
4. The coordinator will be deleting in batches of 50k his alert's history from the database. It will likely take a while to complete (possibly hours) but gradually getting quicker as total result-set decreases.
5. Repeat this process for other alerts that have an extensive alert history.
This issue should be resolved once the Following ERs have been implemented:
200055: As a CA Admin, I would like to improve alert queries by using existing index tables. (This was implemented in version 7.1.1 of Change Auditor)
232582: As a Change Auditor Administrator, I'd like built-in coordinator task to limit alert history.
