system availability
2.Based on the apply mode ofdistributed file system, we did some clustering analysis for the factors which will influence the highavailability issue. Based on the failure and restoring factors, we defined the high availability indistributed file system, and constructed a qualitative analytical model for high availability issue indistributed file system—DFS_HAL ( Distributed File System High Availability Level ) model.
4.Established the resolution model of the non-markov process associated with the system and the availability of the overall system is determined by a function of the reliability and maintainability of each item.
6.The paper gives a brief introduction on structures of the main equipment,system functions,system interface,reliability and availability of TWC system of Teheran Metro Line 1 & 2.
7.The authors implement this model to an online dynamical pet shop system, and prove its availability .
10.The high availability is a basic guarantee of Qos performance of network. So the Oracle RAC 10g system is the best implementation of high availability,as a typical application of Oracle 10g in new grid database.

