If the following applies, you may be impacted by this PRB.

• the loading of Event Management > Dashboard is slow, especially the bottom pane which displays the Alert records
• when you access Transactions (All users) for your transactions and you note that the response times for /ImpactManagerUser.do transactions are high with the bulk of the time spent in SQL time
• you note that there is a large number of records in em_alert_history table (>100,000) and the bulk of the records (>80%) are having Open=false
• your instance is on the New York release

• Install the latest New-York release with Event Management plugin installed
• Access Event Management > Dashboard 

• Please refer to the releases in the "Fixed In" section for the fixed release.
• If the fixed release is not yet available or you are not able to upgrade to a fixed version, as a workaround, please create a record in the Automated Test Framework> Administration > Table Cleanup for table: em_alert_history as below which will clean up the em_alert_history records that are having state is closed and created more than 7 days ago.
• Please remove this Table Cleanup record after you have upgraded to a fixed release.