Abstract: A data processing system having a magnetic disk apparatus that includes a patrol seek system that provides for the altering of a patrol seek method. The patrol seek system provides for the selection of a patrol seek method for executing an optimal patrol seek based on the performance characteristics of a high density magnetic disk apparatus.

Abstract: The database access system of the present invention accesses a hierarchical network type database, treating it as a relational type database. The system analyzes queries in data manipulation language for a relational database which define instructions for retrieval, update, addition and deletion conditions using query analyzing means. According to the analysis result, a record relation tree of the relation among records having the individual fields related to the operation conditions is generated by record relation combining means and stored in storing means. Further, operation conditions are resolved into sets of binary operations using retrieval, update, addition or deletion condition analyzing means so as to generate a condition tree having the operators used in the binary operations as nodes.