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Access path selection in a relational database management system
This paper describes how System R chooses access paths for both simple (single relation) and complex queries (such as joins) given a user specification of desired data as a boolean expression of predicates. Expand
The notions of consistency and predicate locks in a database system
It is argued that a transaction needs to lock a logical rather than a physical subset of the database, and an implementation of predicate locks which satisfies the consistency condition is suggested. Expand
System R: relational approach to database management
This paper contains a description of the overall architecture and design of the system, and emphasizes that System R is a vehicle for research in database architecture, and is not planned as a product. Expand
Granularity of Locks and Degrees of Consistency in a Shared Data Base
A locking protocol which allows simultaneous locking at various granularities by different transactions is presented, based on the introduction of additional lock modes besides the conventional share mode an5 exclusive mode. Expand
SEQUEL 2: A Unified Approach to Data Definition, Manipulation, and Control
SEQUEL 2 is a relational data language that provides a consistent, English keyword-oriented set of facilities for query, data definition, data manipulation, and datac ontrol. SEQUEL 2 may be usedExpand
Granularity of locks in a shared data base
This paper proposes a locking protocol which associates locks with sets of resources. This protocol allows simultaneous locking at various granularities by different transactions. It is based on theExpand
The Recovery Manager of the System R Database Manager
The recovery subsystem of an experimental data management system is described and evaluated and the DO-UNDO-REDO protocol allows new recoverable types and operations to be added to the recovery system. Expand
Efficient and flexible methods for transient versioning of records to avoid locking by read-only transactions
We present efficient and flexible methods which permit read-only transactions that do not mind reading a possibly slightly old, but still consistent, version of the data base to execute withoutExpand
A history and evaluation of System R
The three principal phases of the System R project are described and some of the lessons learned from System R about the design of relational systems and database systems in general are discussed. Expand