I use freeradius and ldap and openvpn in my project. when user disconnect from openvpn,radacct table does not update. I need that acctstoptime updated immediately. please guide me.
We can not easily answer your question in its current form. You need to provide more information.
To help you debugging the issue, you need first to make sure radius accounting is enabled using the appropriate module (ldap, database, etc..).
One other option is to start freeradius server in the foreground in full debug mode using:
This can be done on a testing machine and watching for possible errors when you are making radius requests.