1 / 13

Chapter 3 Data Storage and Access Methods

Chapter 3 Data Storage and Access Methods. Title: Operating Systems Support for Database Management Author: Michael Stonebraker Pages: 217 – 223 Group 01: Esten Rye, DJ Oneil. Overview. Problem Definition Motivation – Why is this Important? Key concepts Buffer Pool Management

rackley
Download Presentation

Chapter 3 Data Storage and Access Methods

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 3Data Storage and Access Methods Title: Operating Systems Support for Database Management Author: Michael Stonebraker Pages: 217 – 223 Group 01: Esten Rye, DJ Oneil

  2. Overview • Problem Definition • Motivation – Why is this Important? • Key concepts • Buffer Pool Management • The File System • Process Scheduling, Management, Inter-process Communication • Consistency Control and Virtual Page File • Validation • Assumptions • Rewrite

  3. Problem Statement • Given • Operating System Services – buffer pool management, file system, scheduling, etc… • Database Management Functions – concurrency, persistence, performance, query, etc… • Objective • Examine applicability of OS services to the support of DBMS functions. • Find • Apparent disconnect between DBMS performance goals and OS design and implementation. • Constraints • OS Services must as reliable as DBMS functions

  4. Why is this Important? • Current Database Management Systems • Usually provide their own versions of OS services. • Make little use of those provided by the OS. • Current Operating Systems • Many services provided by the OS are too slow or inappropriate. • Many OS designers are insensitive to DBMS needs.

  5. Buffer Pool Management • Blocks with a locality of reference remain in cache over repeated reads and writes. • Problems with OS-provided service • Performance Overhead • LRU Replacement performs marginally in a database environment. • Does not guarantee the intentions list and commit flag will be pushed to disk in the proper order.

  6. The File SystemTwo Approaches • Character arrays of dynamically varying size. • File system provided by UNIX • DBMS can provide whatever abstraction it needs on top of this. • Record management system inside the OS. • DBMS wants this approach. • Not always efficient when constructed on top of a character array object.

  7. The File SystemProblems and Limitations • Character Array is not a useful object to a DBMS • Tree Structured File Systems • UNIX implements 2 services using trees • DBMS adds a third tree to support keyed access • One tree with all 3 kinds of information is more efficient. • OS designers should provide DBMS facilities as lower level objects.

  8. Scheduling, Process Management, and Interprocess Communication • Performance • Task switches are inevitable • Task switches are expensive • Critical Sections • Buffer pool is a shared data segment. • De-Scheduling a lock-holding DB process causes problems. • Server model • Multi-Tasking Server • First-Come-First-Serve Server

  9. Consistency Control and Paged Virtual Memory • Consistency Control • Buffer manager cannot be immune from knowledge of transactions. • Buffer manager must maintain its own intentions list • OS functions are duplicated. • Paged Virtual Memory • Possibility of 2 page faults per I/O request • Same problems the buffer pool management has.

  10. Validation • Content is mostly informational. • Based off previous papers and existing implementations of current systems. • Examples are cited primarily from the UNIX OS and the Ingres DBMS. • Issues could be biased and may not be common or applicable to all OS and DBMS combinations.

  11. Assumptions • Presents the topic as one that is applicable to across a number of DBMS and OS • Author constrains his examples to UNIX and Ingres. • Paper was written in 1981. Operating Systems have advanced considerably since then. His points may no longer be applicable.

  12. Changes if Rewritten Today • Increase the diversity of OS and DBMS • Add industry perspective. Are the problems Stonebraker presents really a problem for DBMS designers? • Quantify claims by providing statistical analysis of performance hits.

  13. Questions?

More Related