Use the "Alarm Age-Out Time" functionality located in the "Alarm Management" subview of the VNM model.
Alarm Age-Out Time (hours):
Defines how long an alarm can exist in CA Spectrum. Once an alarm has existed for the number of hours that you specify by this attribute, it is a candidate for automatic removal. To disable this functionality, set this attribute to zero (0).
Every hour, CA Spectrum checks the status of all alarms in the landscape and uses this option to determine whether alarms are cleared. Therefore, an alarm is not removed at the precise moment when its existence time has exceeded the time-out. An alarm can be, at most, an hour “overdue.”
You cannot age out non-user clearable alarms. The system functionality that generates such alarms, clears them. Maintenance Mode, Device Has Stopped Responding, and Management Agent Lost are the non-user clearable alarms.
NOTE: An aged out alarm which is cleared displays the "System.Alarm_AgeOut" value in its corresponding "Cleared By" column under "Cleared Alarms History" tab. The corresponding cleared event also displays this value in its "Cleared By" column under Events tab.