Download DB2 SQL tuning tips for z/OS developers by Tony Andrews PDF

By Tony Andrews

Bankruptcy 1 SQL Optimization best a hundred 1 1. Take Out Any/All Scalar services Coded on Columns in Predicates 2 2. Take Out Any/All arithmetic Coded on Columns in Predicates three three. Code simply the Columns wanted within the decide on part of the SQL assertion four four. steer clear of designated if attainable four five. attempt Rewriting an In Subquery as an Exists Subquery five 6. continually verify Host Variables Are outlined to compare the Columns Datatype 6 7. simply because Or good judgment will be not easy to the Optimizer, test a special Rewrite 6 eight. ensure the info Distribution and different data Are solid and present within the Tables Being Processed eight nine. Use UNION ALL instead of UNION the place attainable nine 10. examine Hardcoding as opposed to utilizing a bunch Variable nine eleven. reduce DB2's SQL Requests eleven 12. try out Rewriting diversity Predicates as among Predicates 12 thirteen. think about using international transitority Tables thirteen 14. supply Prominence to level 1 over level 2 Predicates 14 15. do not forget that the Order of (Some) Predicates Does subject 15 sixteen. Streamline a number of Subqueries sixteen 17. Index Correlated Subqueries 17 18. Get to grasp the DB2 clarify software 17 19. Use instruments for tracking 18 20. hire devote and Restart options 19 21. enforce sturdy Index layout 19 22. keep away from Discrepancies with Non-Column Expressions 20 23. start with All Filtering good judgment outdoors software Code 21 24. make sure that Subquery Predicates related to Min and Max Have the opportunity of Nulls Being lower back dealt with 21 25. consistently Code For Fetch in simple terms or For learn in simple terms with Cursor Processing whilst a question is barely identifying information 22 26. keep away from deciding upon a Row from a desk to aid come to a decision no matter if the common sense within the Code may still Execute an replace or an Insert 23 27. keep away from picking out a Row from a desk in an effort to Get Values for an replace 23 28. utilize Dynamic SQL assertion Caching 23 29. stay away from utilizing decide on * 24 30. beware of Nullable Columns or instances whilst SQL Statements may have Nulls again from the Database supervisor 25 31. reduce the variety of occasions Open and shut Cursors Are finished 25 32. steer clear of now not good judgment in SQL 26 33. Use Correlation IDs for greater clarity 26 34. hold desk and Index records fit and arranged 27 35. reap the benefits of replace the place present of Cursor and Delete the place present of Cursor 27 36. while utilizing Cursors, Use ROWSET Positioning and Fetching utilizing Multiple-Row Fetch, Multiple-Row replace, and Multiple-Row Insert 28 37. be aware of the Locking Isolation degrees 28 38. recognize Null Processing 30 39. continually software with functionality in brain 31 forty. enable SQL Do the paintings 32 forty-one. Code with Lock desk 32 forty two. contemplate OLTP Front-End Processing 33 forty three. think about using Dynamic Scrollable Cursors 34 forty four. make the most of Materialized question Tables to enhance reaction Time (Dynamic SQL basically) 35 forty five. Insert with decide on 37 forty six. make the most of Multiple-Row Fetch 38 forty seven. benefit from Multiple-Row Insert 39 forty eight. make the most of Multiple-Row replace forty forty nine. make the most of Multiple-Row Delete forty two 50. try out Scalar Fullselects in the pick out Clause forty two fifty one. benefit from REOPT as soon as and REOPT automobile in Dynamic SQL and REOPT VARS and REOPT consistently in Static SQL forty three fifty two. establish occasions for risky Tables forty four fifty three. Use the ON dedicate DROP Enhancement forty five fifty four. Use a number of Distincts forty five fifty five. reap the benefits of Backward Index Scanning forty six fifty six. beware of the Like assertion forty six fifty seven. Set Your Clustering Index accurately forty seven fifty eight. Use workforce through Expressions if wanted forty eight fifty nine. beware of Tablespace Scans forty eight 60. don't Ask for What you realize forty nine sixty one. Watch the Order of Tables in a question forty nine sixty two. Use Left Outer Joins Over correct Outer Joins fifty one sixty three. cost for Non-Existence fifty one sixty four. Use saved methods fifty two sixty five. don't opt for a Column for you to style on It fifty three sixty six. regularly restrict the outcome Set if attainable fifty three sixty seven. make the most of DB2 V8 greater DISCARD features by way of Mass Deletes fifty four sixty eight. make the most of the DB2 LOAD software for Mass Inserts fifty four sixty nine. beware of Materialization of perspectives, Nested desk Expressions, and customary desk Expressions fifty five 70. contemplate Compressing facts fifty six seventy one. reflect on Parallelism fifty seven seventy two. continue the STDDEV, STDDEV_SAMP, VAR, and VAR_SAMP capabilities except different features fifty eight seventy three. ponder Direct Row entry utilizing ROWID Datatype (V8) or RID functionality (V9) fifty eight seventy four. try out Your Queries with reasonable facts and a degree of knowledge to mirror functionality matters 60 seventy five. Specify the best Index Columns in the place Clauses sixty one seventy six. Use the place rather than HAVING for Filtering at any time when attainable sixty two seventy seven. consider Index basically Processing at any time when attainable sixty two seventy eight. Index on Expression in DB2 V9 sixty three seventy nine. give some thought to the DB2 V9 Truncate assertion sixty four eighty. Use DB2 V9 Fetch First and Order by means of inside Subqueries sixty five eighty one. benefit from DB2 V9 confident Locking sixty five eighty two. Use the DB2 V9 MERGE assertion sixty six eighty three. comprehend the DB2 NOFOR Precompile alternative sixty eight eighty four. examine pick out Into utilizing Order by way of sixty nine eighty five. Code Boolean time period Predicates at any time when attainable sixty nine 86. attempt Transitive Closure Coding 70 87. keep away from types with Order via seventy one 88. Use Joins rather than Subqueries each time attainable seventy one 89. beware of Case good judgment seventy one ninety. reap the benefits of features within the Order through Clause seventy two ninety one. comprehend Your model of DB2 seventy two ninety two. comprehend Date mathematics seventy three ninety three. be aware of Your High-Volume Insert offerings seventy three ninety four. find out about bypass Locked information (V9) for Lock Avoidance...75 ninety five. style Your enter Streams seventy five ninety six. if you would like precise area of expertise, test the V8 Generate_Unique functionality seventy six ninety seven. recognize the recent suggestions for Declared transitority Tables seventy six ninety eight. be careful whilst Executing Get Diagnostics seventy seven ninety nine. Order Your In record adequately seventy seven a hundred. replace and Delete with decide on (V9) seventy seven a hundred and one. Execute SQL Statements provided that beneficial seventy eight 102. benefit from In-Memory Tables seventy eight 103. avoid Catchall SQL Statements seventy nine 104. steer clear of pointless Sorting seventy nine one zero five. comprehend Expressions and Column features seventy nine 106. be careful while Combining Predicates eighty 107. upload Redundant Predicates to go looking Queries eighty 108. reap the benefits of more suitable Dynamic Caching (V10) eighty one 109. attempt at the moment dedicated for Lock Avoidance (V10) eighty two a hundred and ten. attempt approach Temporal Tables for old facts (V10) eighty three 111. attempt company Temporal Tables for ancient information (V10) eighty five 112. comprehend Your score capabilities (V10) 86 113. benefit from prolonged signs (V10) 87 114. Get higher Timestamp Precision (V10) 88 a hundred and fifteen. try out Index comprises (V10) 89 116. Use With go back to buyer (V10) 89 bankruptcy 2 DB2 SQL tricks ninety one 1. try out the Optimize for 1 Row assertion on the finish of the SQL assertion ninety one 2. upload the A.PKEY = A.PKEY Predicate to the SQL question, the place PKEY Equals the first Key Column of the desk ninety two three. Disqualify an Index selection ninety three four. switch the Order of desk Processing ninety five five. Use disbursed Dynamic SQL ninety six bankruptcy three SQL criteria and instructions ninety nine For COBOL builders ninety nine For All SQL builders 102 bankruptcy four SQL application Walkthroughs 107 bankruptcy five lifestyles Checking 111 instance 1 111 instance 2 113 bankruptcy 6 Runstats a hundred and fifteen bankruptcy 7 preliminary Steps in Tuning a question 117 APPENDIX A Predicate Rewrite Examples 121 Predicate Rewrites: Transitive Closure 122 APPENDIX B DB2 SQL Terminology a hundred twenty five Index 131

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Chapter 10, “pureXML®: Using XML in DB2 for z/OS,” is an entirely new chapter covering DB2’s built-in support for XML data (adding in DB2 V9). And Chapter 11 is another new chapter, “Supporting Temporal Data in DB2 for z/OS,” which covers the new DB2 V10 ability to store, manage, and query temporal data. Finally, Part I concludes with Chapter 12, “DB2 Security, Authorization, and Auditing,” which offers tips on effective security implementation using DB2 data control language. This chapter also delves into recent advancements in DB2 security, including multi-level security, roles and trusted context, SECADM, and database auditing including audit policies.

CLOSE INPUT-DATASET OUTPUT-DATASET. Indeed, many lines that are required in the COBOL program have been eliminated when using SQL. 00. The SQL example obviously is easier to code and maintain because of the limited size of the statement and the set-level processing 1 Must set up IDENTIFICATION and ENVIRONMENT DIVISIONs. DATA DIVISION. FILE-SECTION. Must define input and output files. WORKING-STORAGE SECTION. Must declare all necessary variables. 01 EMPLOYEE-LAYOUT. 05 EMPNO PIC X(6). 05 FIRSTNME PIC X(12).

CHAPTER 1 The Magic Words IN THIS CHAPTER • An Overview of SQL • SQL Tools of the Trade • Static SQL Once upon a time there was a kingdom called Userville. The people in the kingdom were impatient and wanted to know everything about everything—they could never get enough information. Life was difficult and the people were unhappy because data was often lost, and even when it was available, it was often inaccurate and not easy to access. The King decided to purchase DB2, an advanced tool for storing and retrieving data.

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