Browse Prior Art Database

Improved Method to Reserve Values in a Data Base Management System

IP.com Disclosure Number: IPCOM000101929D
Original Publication Date: 1990-Sep-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 55K

Publishing Venue

IBM

Related People

Holm, ML: AUTHOR

Abstract

A data base transaction may remove a row/record and therefore a unique key value used to enforce the uniqueness of a column. Once the value is removed, another job executing a transaction against the same data base may reinsert the value just deleted. If the transaction which removed the value is aborted, the operations performed against the data base must be undone, including the reinsertion of the unique value associated with the row. Since the unique value was inserted by the other transaction, the backout would cause the unique attribute of the column to be violated. Consequently, a technique must be employed to prevent concurrent data base operations from adding a row which contains the unique value until the transaction which deleted it completes.

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Improved Method to Reserve Values in a Data Base Management System

       A data base transaction may remove a row/record and
therefore a unique key value used to enforce the uniqueness of a
column.  Once the value is removed, another job executing a
transaction against the same data base may reinsert the value just
deleted.  If the transaction which removed the value is aborted, the
operations performed against the data base must be undone, including
the reinsertion of the unique value associated with the row. Since
the unique value was inserted by the other transaction, the backout
would cause the unique attribute of the column to be violated.
Consequently, a technique must be employed to prevent concurrent data
base operations from adding a row which contains the unique value
until the transaction which deleted it completes.  Besides
uniqueness, other inter-record constraints imposed upon the data base
must also be enforced.

      To inhibit another job from using a particular value, it must
somehow be reserved until the transaction which depends on being able
to reinsert it either finishes or aborts.

      One method to reserve values is to keep another data structure
around (e.g., an index) to hold the values.  Any other transaction
which adds values to the unique index must then search the associated
data structure to ensure it will not violate a uniqueness constraint.

      Instead of maintaining a separate index to reserve values
associated w...