Data access system for a file access processor

Abstract

A Data Access System for a File Access Processor for servicing requests from a set of Application Support Processors, which can exist in a global network, with each Application Support Processor sharing access to data in files stored by the File Access Processor. The File Access Processor manages access to a set of data files and information about files held in file directories, which allow for managing file collections, can relate to each other hierarchically, and may be shared. Each Application Support Processor also maintains therein an internal cache of file information to improve performance by reducing communications required with the File Access Processor for information about files. The File Access Processor provides the Application Support Processors with information for updating and maintenance of local caches of directory and file description information through a centralized accumulation and distribution of cache change notifications. The Data Access System also provides for permanent storage in the form of catalogs for retaining shared information about files, directories, and control information. A separate access method and storage facility is utilized for these catalogs from that utilized for file data, permitting flexibility in access to catalog information which require access only occasionally, while retaining high performance in the access to file data.