Accounting requests and LDAP relation

Dear All, Is there any relation between the accounting requests and the LDAP, in case i'm using LDAP for authentication and MySql for accounting. Now i have many accounting requests and my DB machine is loaded , but what i can't understand is why my LDAP machine is loaded too. i make a debug on the RADIUS and found that when handling the accounting request the RADIUS contacts the sql and ldap to check GroupMember, in sql.conf i commented the group member query and nothing happens against the MySql , but still happens against the LDAP . any idea ??? thanks all