Check Radius Server Changes

Hi I’m a software developer and creating a JAVA program to manage WiFi Codes.

The application manage the Database of a Radius Server on which i have connect the MikroTik.

The problem is when I disconnect a user (delete him from active users). Mikrotik still keeps him online.

I want Mikrotik to check more often the Radius Server, so after i disconnect or delete a user from the database , Mikrotik delete him from active users.

your RADIUS server should support RADIUS incoming feature and then enable the support for that on the router as well:
http://wiki.mikrotik.com/wiki/Manual:RADIUS_Client#Connection_Terminating_from_RADIUS