An application method of On-line Charging 
System in 
Arrears Risk Control System: 1) The subsystem of OCS, Mediation, communicates with CC 
Client, receives a credit control request raised by the CC 
Client and processes with a fault-tolerant management. 2) The Credit Control analyses call request, identifies a 
type of service and request, selects necessary service 
transaction logic, and judges an authorized quota of the service, after receiving the quota, the Credit Control requests for real time forward modeling from the Rating. 3) After receiving a price of the service, the Credit Control requests real 
time inversion from the Rating and meanwhile transfers the price to the Rating. 4) The Rating requests account comparison from the Account after receiving the price. 5) The Account compares the price with a customer's account information to make decision of subsistence lock, if there is enough balance in the account, then the fee of the price will be deducted from the balance and then locked. 6) The Account returns the account information of the compared result. 7) The Rating inverses the 
authorization amount according to the compared result returned by the Account, and send back to the Credit Control. 8) The Credit Control constructs a service relevant responding 
package according to the 
authorization amount, and sends the responding 
package to the Mediation to complete the OCS 
processing flow.