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Method, System and Program for Implementing Dynamic Scrollable Cursors in a Database

IP.com Disclosure Number: IPCOM000031862D
Original Publication Date: 2004-Oct-14
Included in the Prior Art Database: 2004-Oct-14
Document File: 1 page(s) / 29K

Publishing Venue

IBM

Abstract

Method, System and Program for Implementing Dynamic Scrollable Cursors in a Database

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Method, System and Program for Implementing Dynamic Scrollable Cursors in a Database

Background: Today, DB2 of OS/390 and z/OS provides static scrollable cursors. However, static scrollable cursors restrict the applications from being able to fetch newly inserted rows. Furthermore, they require extra disk storage to save the temporary result table per transaction. While some applications prefer to work with a fixed set of rows, at the expense of extra disk storage, there is also an extensive requirement in the industry to be able to scroll on the database table, there by having immediate access to the most current data.

Problem: Since newly inserted rows and new updates are required to be seen, a method must be devised to fetch directly from the database table rather than a temporary copy of the result table. The method must also include the capability to scroll on the database table via all the allowable fetch orientation methods.

Solution: The problem is solved by creating logic to support backward scan, similar to forward scan, using the access path ( tablespace scan or index scan) chosen by the database optimizer to fetch requested rows via a dynamic scrollable cursor. The backward scan must be sensitive to committed inserts, updates and deletes made by other transactions as well as uncommitted changes from the same transaction.

With the table space scan access path, dynamic scrollable cursors return rows in physical sequence as they are arranged in the data...