Execute some action when user terminate session

Hi. I need to perform several queries on radacct to make statistics about user connection, duration and so on. Since executing some queries can be time consuming it's not advisable that I run them on the radius database, so I'm considering copying all or some informations from radacct somewhere else. So, the question is: is it possible to perform some action when an user session is terminated? Or: is there any better solution which doesn't involve data duplication? Thanks.