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System R is a database management system which provides a high level relational data interface. The systems provides a high level of data independence by isolating the end user as much as possible from underlying storage structures. The system permits definition of a variety of relational views on common underlying data. Data control features are provided,(More)
The recovery subsystem of an experimental data management system is described and evaluated. The transactmn concept allows application programs to commit, abort, or partially undo their effects. The DO-UNDO-REDO protocol allows new recoverable types and operations to be added to the recovery system Apphcation programs can record data m the transaction log(More)
CONVOYS DESCRIBED When driving on a two-lane road with no passing one often encounters clusters of cars. This is because a fast-moving car will soon bump into a slow one. The equilibrium state of such a system is for everyone to be in a convoy behind the slowest car. In System R [Astrahan], transactions often bump into one another when contending for shared(More)
Sequences of character strings with an order relation imposed between sequences are considered. An encoding scheme is described which produces a single, order-preserving string from a sequence of strings. The original sequence can be recovered from the encoded string, and one sequence of strings precedes another if and only if the encoding of the first(More)
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