Research Of Distributed Database Resource's High Availability

With the popular application of distributed database systems in business sections, providing the high availability(HA) service became very important. Database resource's HA could be defined that a main data resource provide durative service and a backup data resource could take over all tasks and services in a short time when the main resource failed. Therefore, the entire system may still be available and users would not be aware of switching of nodes.Deadlock in concurrency control was an important problem which should be resolved by distributed systems. Moreover, it was also an important factor of causing unavailability. Distributed databases in existence usually adopt lock mode to implement concurrency control, in via of canceling transaction to break through deadlock loop. However, some kind of deadlock may still appear due to the granularity switch based on multi-granularity mode.In the HA mode Design, including Data Communications Layer, Date Resource Configure Layer, Scout Layer, Database State Control Layer, Command Switch Layer, Log Layer, etc. In this dissertation, it focuses on the research of log style, log format, log space, log synchronization and log recovery in heterogeneous database system.The log recovery mechanisms based on data redundant is a important quomodo to implement distributed database resource's HA. In such a system, all of share data resources will build one or more duplicates according to user's need. Log could be used to maintain consistency among duplicates. So, Log became the most popular and reliable technique to maintain system High Availability.