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Static SQL and Access Path Review Tips and Tricks. Paul Walters Sallie Mae Inc. Paul.A.Walters@Salliemae.com Session Code: E05 May 12, 2010 • 08:30 a.m. – 9:30a.m. Platform: DB2 zOS. Agenda . Managing Change Data to Review Plan Tables Objects Statistics SQL Statements Key Indicators

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static sql and access path review tips and tricks

Static SQL and Access Path ReviewTips and Tricks

Paul Walters

Sallie Mae Inc.

Paul.A.Walters@Salliemae.com

Session Code: E05

May 12, 2010 • 08:30 a.m. – 9:30a.m.

Platform: DB2 zOS

agenda
Agenda
  • Managing Change
  • Data to Review
    • Plan Tables
    • Objects
    • Statistics
    • SQL Statements
    • Key Indicators
  • Statistics and System Changes
  • Application Changes
  • Best Practices
  • Plan Stability DB2 V9
slide3

Brief History

  • How did we get here?

Managing Change – Types of Changes & Preserving Performance

  • DB2 Changes
  • ZPARM Changes
  • Statistics Changes
  • DDL Changes
  • Application Changes

Plan Tables to the Rescue

E

basic explain
Basic Explain

DSNWFQB##

DSNBFQB##

DSNVT##/V9

QUERYNO

O

explain information by access
Explain information by Access

SELECT *

FROM SYSIBM.SYSDUMMY1

WHERE 1 = 2

a complete picture
A Complete Picture

Program Execution

Function

Catalog Statistic

PT

plan tables most familiar
Plan Tables (Most familiar)

DB2 V9 adds

PARENT_PLANNO

  • PLAN_TABLE
    • Contains most of the access path selection information that was gathered when the package was bound with EXPLAIN(YES).
  • DSN_STATEMNT_TABLE
    • Contains COST_CATEGORY, REASON AND costing information PROCSU, PROCMS. The costing numbers are ESTIMATED and can very widely with changes to DB2.

DB2 V9 adds a TOTAL_COST

plan tables continued
Plan Tables (Continued)
  • DSN_FILTER_TABLE
    • Contains information on what stage the predicate is processed (MATCHING, SCREENING, STAGE1 and STAGE2).
  • DSN_PREDICAT_TABLE
    • Contains FILTERFACTOR, BOOLEAN_TERM indicator and the actual predicate text.
  • DSN_DETCOST_TABLE
    • Contains detailed cost information (COMPCOST) at each step of the access path (mini plan), an estimate on the number of rows that will be returned after the local predicates are applied (ONECOMPROW) and an estimate of rows returned from DM and RDS (DMROWS,RDSROW).

Q

dsn predicat table
DSN_PREDICAT_TABLE
  • DSN_PREDICAT_TABLE and SYSCOLUMNS and SYSKEYS provide information helpful for index review
plan tables continued1
Plan Tables (Continued)
  • DSN_VIRTUAL_INDEXES
    • This table allows for the creation or deletion of indexes virtually. This enables a query to be explained with the virtual change.
  • 10 other EXPLAIN Tables
    • The additional tables support Explain statements from the dynamic statement cache, sort operations or other Explain details.
slide19

Objects

Object Structure and Buffer Pool Assignments

Statistics

DB2 Statistics and Real Time Statistics

Package Execution/Function

managing change statistics and system changes
Managing Change: Statistics and System Changes
  • DB2 V9 Enhancements that require rebinds:
    • Puffing of the runtime structures – especially with RELEASE(COMMIT)
    • Required to reestablish SPROCs (with no rebind a 0-10% performance penalty )
    • Virtual Storage Constraint Relief
    • Global Query Optimization
    • Sort Avoidance with Distinct and Group By

You bought it might as well drive it

managing change statistics and system changes1
Managing Change: Statistics and System Changes

Release Guide

Hold Data

  • Impacts on Access Path Selection
  • Identification
    • Model a Control set of structures Off Production
    • Copy Production DBRMS
    • Bind Before and After Maintenance
    • Review Changes

PROCMS

PROCSU

managing change statistics and system changes2
Managing Change: Statistics and System Changes

I001 No Change

W001 C<P Steps

W002 C>P Steps

W005 Change

W003 C<P Stmts

W004 C>P Stmts

W006 New Package

managing change statistics and system changes3

PERFORMANC

E

Managing Change: Statistics and System Changes
  • Managing Rebinds During Upgrades
    • Wait until the upgrade is stabilized
    • Rebind the safe and improved packages with PLANMGMT
    • Execute RUNSTATS – focus on heavily used objects, watch for changes in CLUSTERRATIOF, use “_HIST” tables
    • Check Access Path Changes with new statistics
    • Rebind Previously Untouched Packages
    • Rebind packages bound before new statistics were collected
managing change application changes
Managing Change: Application changes
  • New/Changed Packages
    • New programs Require top down review
    • Changed Programs – look for new objects and/or access path changes
  • New/Changed Objects

I001 No Change

W001 C<P Steps

W002 C>P Steps

W003 C<P Stmts

W004 C>P Stmts

W005 Change

W006 New Package

plan stability db2 v9
Plan Stability DB2 V9
  • Provides a backup of a access path that can be used for fallback
  • Enabled Globally with ZPARM PLNMGNT or at bind time with PLNMGNT option.
    • Information Stored in SPT01 and SYSPACKDEP
    • Rebind Switch
    • Each Copy is Separately Invalidated
    • Only Current information is stored in SYSPACKAGE
    • Dependant versions recorded in SYSPACKDEP(DTYPE P,O)
    • Can only replace the entire package
    • How Stale is the Original Copy
  • DB2 Hints are still Relevant
other db2 v9 changes
Other DB2 V9 Changes
  • Virtual Indexes – available via APAR in V8 (PK46687)
  • Unicode Plan Tables (PK85068)
  • New Explain Sub-Query Parent Query Block
  • Visual Explain is Deprecated in DB2 V9
  • Optimization Service Center (OSC) Deprecated in the next Release of DB2
  • IBM Data Studio is the replacement for OSC
best practices
Best Practices
  • Explain(YES)
  • Regular Review
  • Know Your Applications
slide28

WITH STMT1(COLLID,PROGNAME,BIND_TIME) AS

(SELECT COLLID,NAME,MAX(BINDTIME)

FROM SYSIBM.SYSPACKAGE

WHERE LOCATION = ' '

AND BINDTIME > CURRENT TIMESTAMP - 84 HOURS

AND TYPE <> 'T' AND EXPLAIN = 'Y'

AND (COLLID LIKE 'PLSF%')

GROUP BY COLLID,NAME )

,STMT2(COLLID,PROGNAME,BIND_TIME) AS

(SELECT S1.COLLID,S1.PROGNAME,

COALESCE(MAX(PT.BIND_TIME),'0001-01-01-00.00.00.000000')

FROM PDBA0.PLAN_TABLE AS PT, STMT1 AS S1

WHERE PT.COLLID = S1.COLLID

AND PT.PROGNAME = S1.PROGNAME

AND PT.BIND_TIME < S1.BIND_TIME

AND PT.OPTHINT = ' '

GROUP BY S1.COLLID,S1.PROGNAME)

Identify Packages BINDTIME with Explain Yes and

The previous BIND_TIME from the Plan_Table

slide29

,STMT_REV(COLLID,PROGNAME,BIND_TIME,CSCNT,CPCNT,

PSCNT,PPCNT,WARNING) AS

(SELECT COLLID,PROGNAME,BIND_TIME

,SUM(CSCNT) AS CSCNT ,SUM(CPCNT) AS CPCNT

,SUM(PSCNT) AS PSCNT ,SUM(PPCNT) AS PPCNT

,CASE WHEN SUM(PSCNT) = 0 THEN 'W006'

WHEN SUM(CSCNT) > SUM(PSCNT) THEN 'W004'

WHEN SUM(CSCNT) < SUM(PSCNT) THEN 'W003'

WHEN SUM(CPCNT) > SUM(PPCNT) THEN 'W002'

WHEN SUM(CPCNT) < SUM(PPCNT) THEN 'W001'

ELSE NULL END AS WARNING FROM

First Cut

W001 C<P Steps

W002 C>P Steps

W003 C<P Stmts

W004 C>P Stmts

W006 New Package

slide30

Total Steps and Statements from the Current and Previous Explain output

(SELECT S1.COLLID,S1.PROGNAME,S1.BIND_TIME

,COUNT(DISTINCT QUERYNO) AS CSCNT,COUNT(*) AS CPCNT

,0 AS PSCNT ,0 AS PPCNT

FROM STMT1 AS S1, PDBA0.PLAN_TABLE AS PT

WHERE PT.PROGNAME = S1.PROGNAME

AND PT.COLLID = S1.COLLID

AND PT.BIND_TIME = S1.BIND_TIME AND PT.OPTHINT = ' '

GROUP BY S1.COLLID,S1.PROGNAME,S1.BIND_TIME

UNION ALL

SELECT S1.COLLID,S1.PROGNAME,S1.BIND_TIME

,0 AS CSCNT ,0 AS CPCNT

,COUNT(DISTINCT QUERYNO) AS PSCNT ,COUNT(*) AS PPCNT

FROM STMT1 AS S1, STMT2 AS S2, PDBA0.PLAN_TABLE AS PT

WHERE PT.PROGNAME = S2.PROGNAME

AND PT.COLLID = S2.COLLID

AND S1.PROGNAME = S2.PROGNAME

AND S1.COLLID = S2.COLLID

AND PT.BIND_TIME = S2.BIND_TIME AND PT.OPTHINT = ' '

GROUP BY S1.COLLID,S1.PROGNAME,S1.BIND_TIME ) AS DATA

GROUP BY COLLID,PROGNAME,BIND_TIME)

slide31

,CDATA(COLLID,PROGNAME,BIND_TIME,

SEQ ,QUERYNO,QBLOCKNO,PLANNO,MIXOPSEQ,DATA) AS

(SELECT S1.COLLID,S1.PROGNAME,S1.BIND_TIME,

CSEQ.SEQ ,QUERYNO ,QBLOCKNO ,PLANNO ,MIXOPSEQ,

{COLUMN1 CONCAT COLUMN2….}

FROM STMT1 AS S1, PDBA0.PLAN_TABLE AS PT,

TABLE (SELECT COUNT(*)+1 AS SEQ

FROM PDBA0.PLAN_TABLE AS PT1

WHERE PT.PROGNAME = PT1.PROGNAME

AND PT.COLLID = PT1.COLLID

AND PT.BIND_TIME = PT1.BIND_TIME

AND PT.OPTHINT = PT1.OPTHINT

AND DIGITS(PT.QUERYNO) CONCAT DIGITS(PT.QBLOCKNO) CONCAT

DIGITS(PT.PLANNO) CONCAT DIGITS(PT.MIXOPSEQ) >

DIGITS(PT1.QUERYNO) CONCAT DIGITS(PT1.QBLOCKNO) CONCAT

DIGITS(PT1.PLANNO) CONCAT DIGITS(PT1.MIXOPSEQ) ) AS CSEQ

WHERE PT.PROGNAME = S1.PROGNAME

AND PT.COLLID = S1.COLLID

AND PT.BIND_TIME = S1.BIND_TIME

AND PT.OPTHINT = ' ')

Select the Current Explain Data with a New Sequence Number

slide32

,PDATA(COLLID,PROGNAME,

SEQ ,QUERYNO ,QBLOCKNO ,PLANNO ,MIXOPSEQ, DATA) AS

(SELECT S2.COLLID,S2.PROGNAME,

PSEQ.SEQ ,QUERYNO ,QBLOCKNO ,PLANNO ,MIXOPSEQ ,

{COLUMN1 CONCAT COLUMN2….}

FROM STMT2 AS S2, PDBA0.PLAN_TABLE AS PT,

TABLE (SELECT COUNT(*)+1 AS SEQ

FROM PDBA0.PLAN_TABLE AS PT1

WHERE PT.PROGNAME = PT1.PROGNAME

AND PT.COLLID = PT1.COLLID

AND PT.BIND_TIME = PT1.BIND_TIME

AND PT.OPTHINT = PT1.OPTHINT

AND DIGITS(PT.QUERYNO) CONCAT DIGITS(PT.QBLOCKNO) CONCAT

DIGITS(PT.PLANNO) CONCAT DIGITS(PT.MIXOPSEQ) >

DIGITS(PT1.QUERYNO) CONCAT DIGITS(PT1.QBLOCKNO) CONCAT

DIGITS(PT1.PLANNO) CONCAT DIGITS(PT1.MIXOPSEQ) ) AS PSEQ

WHERE PT.PROGNAME = S2.PROGNAME

AND PT.COLLID = S2.COLLID

AND PT.BIND_TIME = S2.BIND_TIME

AND PT.OPTHINT = ' ')

Select the Previous Explain Data with a New Sequence Number

slide33

SELECT CHAR(C.COLLID,10) AS COLLID ,CHAR(C.PROGNAME,10) AS PROGNAME

C.BIND_TIME,

CASE WHEN SR.WARNING IS NULL AND C.DATA <> P.DATA THEN C.SEQ

ELSE 0 END AS SEQ,

CASE WHEN SR.WARNING IS NULL AND C.DATA <> P.DATA THEN 'W005'

ELSE SR.WARNING END AS WARNING

,SR.CSCNT,SR.CPCNT, SR.PSCNT,SR.PPCNT,

CASE WHEN SR.WARNING IS NULL AND C.DATA <> P.DATA THEN C.QUERYNO

ELSE 0 END AS QUERYNO,

CASE WHEN SR.WARNING IS NULL AND C.DATA <> P.DATA THEN C.QBLOCKNO

ELSE 0 END AS QBLOCKNO,

CASE WHEN SR.WARNING IS NULL AND C.DATA <> P.DATA THEN C.PLANNO

ELSE 0 END AS PLANNO,

CASE WHEN SR.WARNING IS NULL AND C.DATA <> P.DATA THEN C.MIXOPSEQ

ELSE 0 END AS MIXOPSEQ FROM CDATA AS C

LEFT OUTER JOIN PDATA AS P ON P.COLLID = C.COLLID AND

P.PROGNAME = C.PROGNAME AND P.SEQ = C.SEQ

INNER JOIN STMT_REV AS SR ON SR.COLLID = C.COLLID AND

SR.PROGNAME = C.PROGNAME AND SR.BIND_TIME = C.BIND_TIME

WHERE (C.DATA <> P.DATA OR WARNING IS NOT NULL)

slide34

UNION

SELECT CHAR(C.COLLID,10) AS COLLID ,CHAR(C.PROGNAME,10) AS PROGNAME,

C.BIND_TIME

,0 AS SEQ, 'I001' AS WARNING ,SR.CSCNT,SR.PSCNT, SR.CPCNT,SR.PPCNT

, 0 AS QUERYNO, 0 AS QBLOCKNO, 0 AS PLANNO, 0 AS MIXOPSEQ

FROM CDATA AS C

INNER JOIN STMT_REV AS SR ON

SR.COLLID = C.COLLID AND

SR.PROGNAME = C.PROGNAME AND

SR.BIND_TIME = C.BIND_TIME

WHERE WARNING IS NULL

AND NOT EXISTS (SELECT 1

FROM PDATA AS P

WHERE P.COLLID = C.COLLID AND

P.PROGNAME = C.PROGNAME AND

P.SEQ = C.SEQ AND

P.DATA <> C.DATA)

ORDER BY 3 DESC

FOR FETCH ONLY WITH UR

UNION the Remainder/Unchanged Packages

reference material
Reference Material
  • Redbooks
    • Data Integrity with DB2 for z/OS
    • DB2 9 for z/OS Performance Topics
  • Manuals
    • DB2 V9 Performance Monitoring and Tuning Guide
  • Web
    • DB2 for z/OS Exchange at IBM.COM  
    • WWW.IDUG.ORG
session e05 static sql and access path review tips and tricks
Session: E05Static SQL and Access Path ReviewTips and Tricks

Paul Walters

Sallie Mae Inc.Paul.A.Walters@Salliemae.com