Database systems: The Intelligent Store: A content-addressable page manager

The Intelligent Store (IS) is a page manager for an experimental local computer network. Typical clients of the IS are a database manager or a file manager. The IS provides concurrent, transaction-oriented, read-write-search access to a large database of pages. The IS ensures that committing a transaction is atomic and permanent, in spite of crashes. The IS allows multiple, concurrent readers and writers. Rather than using conventional wait-until-available locking, the IS uses an optimistic locking policy. That is, the IS always allows transactions to proceed, assuming they will not interfere. If two transactions do interfere (e.g., if they both write the same page), the IS aborts one of them. This paper gives some analytic results for the interference probability. Two implementations of the IS exist. The first was designed to use one or more content-addressable disks. By reading all tracks in a cylinder in parallel, and filtering each stream, such a device can search an entire cylinder in one disk revolution. This version of the IS uses the content-addressable features internally, as well as making them available to its clients. Unfortunately, suitable content-addressable disks are not commercially available. Therefore, a second implementation of the IS was designed to use conventional disks. The two versions of the IS present the same interface to their clients, except that the conventional-disk IS does not provide search access.