Metadata Service For Database System On The Grid

Currently, research and development activities relating to the Grid generally focus on applications where data is stored in files. However, database system has a central role in data storage, access, organization, etc, for numerous applications.GbdAdmin aims to realize the access and integration of the database resources on the Grid, hiding the distribution of the database system, heterogeneity of the inner data schemas and complexity of the operations. In order to access to database transparently, GdbAdmin provides a virtual global logical database view for the users, which manages and coordinates the database resources.Metadata service is one of the critical issues in the research of the database access and integration on the Grid. Metadata is the description of the capabilities of a database service and the accessed data information, which is other Grid services and applications relied on to integrate the database services. It is the key to transparent distribution, storage and management of the database resources. MDS(MetaData Service) utilizes the layered distribution structure, and provides both the metadata management and database service discovery. Metadata management includes registry, access and manage the metadata. And it implements the mapping of the logical metadata to the physical metadata. So the system can access to the database resources on the Grid transparently. The service log is adopted to improve the searching performance of the available database services. The access frequency based service discovery mechanism and the replacement factor based replacement algorithm are put forward. The service log replacement algorithm takes not only the access count but also the access frequency into account when calculating the replacement factor of the database service objects, which drastically enhances the hit rate of the service discovery.