Hi Keith,

You shouldn't need to delete/purge anything when you see the "Low Water Mark" alert. The one you would need to be more concerned about is the "High Water Mark"

In CCM you set the Automatic purge to take place automatically @ 2 million records or if you don't want to consume the whole 6 gig CAR Database maximum you can set a High water mark (maximum percentage of the 6-gigabyte CAR database that you want the system to use for CAR data. )

When the purge takes place CAR looks at the setting "Min Age of Call Detail Records" to ensure that records are saved for this minimum time frame. You may always want a minimum of 60 days of CDR records (for Billing purposes perhaps) so you would enter 60 for this setting :) all records older than 60 days would be purged at this point.

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/service/5_1_3/car/carsycfg.html#wp1212660

Hope this helps!

Rob