Runstats and Reorg

7/27/2019 Runstats and Reorg

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Gabrielle & Associates, http://www.GabrielleDB2.com, (972)412-8866, Copyright 1984, 2004 - All Rights Reserved RR 1

Runstats

and

Reorganization


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Table of Contents

Why and When to Collect Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Scheduling Runstats, Reorg, & Rebind . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Catalog Tables Updated by RUNSTATS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Collecting Statistics on Non-Indexed Columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

When to Reorganize Using the Catalog . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Online REORG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47

Incremental Update of Shadow Copy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

REORG with SORTKEYS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

REORG with Inline COPY and STATISTICS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

Unloading Rows Using REORG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

REORG INDEX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92

Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

Appendix A: Reorg Catalog & Directory Tablespaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

Exercises . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109


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Why and When to Collect Statistics

Why collect statistics

Performance improvements for static, dynamic SQL, and reoptimization< Particular important for changing cluster ratios, skewed distribution of values, low

cardinality columns, and range predicates

< Non-indexed column statistics are used for:

S Local predicates in determining the join method and the inner and outer table of thejoin

SNon-leading columns of a composite index when equal predicates are not specified onall columns and more cases expected in future

Provide the optimizer with current statistics for generating an efficient access path Monitor and tune database, plans and packages

< Determine reorganization needs, space management, current documentation

When to collect statistics After a table and indexes have been created and the data loaded After a tablespace or index has been reorganized and statistics have changed significantly After heavy insert, update, and delete activity Before binding and rebinding plans and packages Before monitoring catalog tables

When to collect statistics with utility processing (V6)

During LOAD processing During REORG processing when needed and if additional costs are acceptable During REBUILD INDEX processing if needed Can specify most RUNSTATS parameters to these utilities


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Timings of a SELECT Before/After RUNSTATS (V1.2)

Timings

3090/200 CPU BeforeRUNSTATS

AfterRUNSTATS

CPU Time > 20 Minutes 1.29 Seconds

Elapsed Time > 75 Minutes 9.14 Seconds

List all customers who do not have accounts

Customer table has 1,100 rows< Unique index on primary key of CUST NO

Account table has 42,000 rows< Index on foreign key of CUST NO

SELECT CT.CUST NO, CUST NAMEFROM CUST TAB CT

WHERE NOT EXISTS(SELECT AT.CUST NOFROM ACCT TAB ATWHERE CT.CUST NO = AT.CUST NO);


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Default Statistics Used by the Optimizer

If RUNSTATS has not been executed,< Default statistics are used by the optimizer

SYSIBM.SYSTABLES

CARDF 10,000 rows

NPAGESF 501 = CEILING(1 + CARDF / 20)

PCTROWCOMP 0

EDPROC blank = EDITPROC not used

SYSIBM.SYSINDEXES

CLUSTER-RATIOF

0 (95 % IF CLUSTERED = Y)

CLUSTERED Y if CLUSTER used when index was created

FIRSTKEY-CARDF

25

FULLKEY-CARDF

25

NLEAF 33 = CARDF / 300

NLEVELS 2

SYSIBM.SYSCOLUMNS

COLCARDF 25FOREIGNKEY B for SBCS (Single Byte Character Set)

SYSIBM.SYSTABLESPACE

NACTIVEF 501 = CEILING(1 + CARDF / 20)

Uniform distribution of data assumed

Same default statistics are used for the "STATS" tables with partitioned tablespaces to be discussed


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Catalog Tables in DSNDB06 and SYSHIST Databases

DSNDB06 database contains the catalog tables used by DB2

SYSHIST database can contain a history of most statistics collected by RUNSTATS if requestedwith the HISTORY parameter (V7)

Can accumulate a history of statistics over time in:< SYSIBM.SYSCOLDIST_HIST

< SYSIBM.SYSCOLUMNS_HIST< SYSIBM.SYSINDEXES_HIST

< SYSIBM.SYSINDEXPART_HIST

< SYSIBM.SYSINDEXSTATS_HIST

< SYSIBM.SYSLOBSTATS_HIST

< SYSIBM.SYSTABLEPART_HIST

< SYSIBM.SYSTABLES_HIST< SYSIBM.SYSTABSTATS_HIST

Can insert, update, and delete the history catalog tables

MODIFY STATISTICS utility can be used to clear out the history statistics


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Scheduling Runstats, Reorg, & Rebind

Avoid using a divining rod

Execute RUNSTATS with the HISTORY parameter periodically, for example,< Daily, weekly, monthly, etc.

Collect statistics inline using LOAD and REORG< Good alternative

Analyze changes in statistics over time and update cycles

VOLATILE can be specified when table is created or added with alter (V8)< Optimizer is very likely to choose to use an index

< Useful for tables that vary in size and other statistics throughout the day, week, etc.

Schedule RUNSTATS, REORG, and rebinds as indicated by analysis

Alternative - Use utility thresholds, develop or purchase software to submit utilities as requiredbased on statistics in the catalog tables

< Beware of automatically submitting utilities taking more time than batch window allows


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Growth in the Number of Rows and Space

6 Assume history statistics have been collected over a period of time (weeks, months, etc. forexample)< Constant growth rate over time period

< Statistics can be cleared using MODIFY STATISTICS utility and collected over another

period of time

SELECT MAX(CARDF) AS MAXCARDF, MIN(CARDF) AS MINCARDF,

((MAX(CARDF) - MIN(CARDF)) * 100 / MIN(CARDF)AS PGROW,(DAYS(MAX(STATSTIME)) - DAYS(MIN(STATSTIME)) AS NDAYS)

FROM SYSIBM.SYSTABLEPART_HISTWHERE DBNAME = 'DASPJDB'AND TSNAME = 'DASPJTSP';

Alternative - Can do an analysis based on space rather than the number of rows,< Do similar calculations using SPACEF rather than CARDF


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Estimate Pages Changed

Determine the % of changed pages between 3 full image copies6Assume random changesS Otherwise, analysis suggests executing RUNSTATS more often than neededSELECT C.TIMESTAMP, C.DBNAME, C.TSNAME, C.NPAGESF, C.CPAGESFFROM SYSIBM.SYSCOPY AS C, SYSIBM.SYSTABLESPACE AS TWHERE DBNAME = 'DASPJDB'AND TSNAME = 'DASPJTSP'AND ICTYPE = 'F'

AND C.TIMESTAMP > T.STATSTIME;

Imagecopy

NPAGESF/Integer

CPAGESF/Integer

% Changed % AfterSubtraction

1 1.00E+02100

1.00E+0110

(10/100) * 100 = 10 10

2 1.00E+02100 1.50E+0115 (15/100) * 100 = 15 +(15/100)-((10 %)*(15/100))= 23.5

3 1.00E+02100

5.00E+005

(5/100) * 100 = 5 +( 5/100)-((23.5%)*( 5/100))= 27.3

C.NPAGESF = number of pages in image copy

C.CPAGESF = number of changed pages in image copy

"% Changed" column shows percentage of changed pages since the previous image copy

"% After Subtraction" column shows the formula and results of adjusting for the possibilitythat changes were made at random and the same pages were copied twice

% of changed pages with or without subtractions can be considered in scheduling RUNSTATS,

REORG, and REBIND


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Scheduling Runstats, Reorg, & Rebind

Executing RUNSTATS has no effect on performance after static plans/packages with

NOREOPT(VARS) have been bound< Static SQL with REOPT(VARS) and dynamic SQL see statistic with each access path

selection

Rebind plans and packages in conjunction with REORG/RUNSTATS if statistics have changed> 20 % and changes are disproportionate, particularly:

< NLEAF, NPAGESF, NACTIVEF< Table, partition, index, and column cardinalities

< CLUSTERRATIOF and FREQUENCYF

< Range of HIGH2KEY and LOW2KEY

< NLEVELS > 2 and increases by >=1

Alternative - analyze changes in paths chosen in test PLAN TABLE to determine if rebinds arenecessary in production

RUNSTATS and rebinds need not be done frequently in most cases

It is worth 1-2-3 days of analysis for a system to

be in production 5-10-15 years< All your ducks will be in a row

STATSTIME column in catalog tables updated by RUNSTATS contains the timestamp of whenstatistics were updated


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Catalog Tables Updated by RUNSTATS and Used by the Optimizer

SYSIBM.SYSTABLES

CARDF Number of rows in the table from tablespace scan

NPAGESF Number of pages that contain rows of the table fromtablespace scan

PCTROWCOMP Percentage of rows compressed in table from tablespacescan * 100

EDPROC blank = EDITPROC not used

SYSIBM.SYSCOLUMNS

COLCARDF Estimated number of distinct values in column fromtablespace scan or scan of leaf pages if column isindexed

HIGH2KEY First 8 bytes of second highest value in the columncollected like COLCARDF

LOW2KEY First 8 bytes of second lowest value in the columncollected like COLCARDF

SYSIBM.SYSINDEXESCLUSTER-RATIOF

Percentage of rows in clustering sequence from leaf pages* 100. Counted if RID >= RID from previous RID pair andfunction applied

CLUSTERED Y if >=95 % of rows in sequence from CLUSTERRATIOF

FIRSTKEY-CARDF

Number of distinct values of the first key column fromleaf pages

FULLKEY-CARDF Number of distinct values of the full key from leaf pages

NLEAF Number of active leaf pages in the index from leaf pages

NLEVELS Number of levels in the index tree from traversing index

SYSIBM.SYSTABLESPACE

NACTIVEF Number of active pages in the tablespace from HURBA (HighUsed RBA) in VSAM/ICF catalog.


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Partition Statistics Collected like Nonpartitioned Statistics

SYSIBM.SYSTABSTATS

CARDF~ Number of rows in partition

NPAGESF~ Number of pages that contain rows in the partition

PCTROWCOMP Percentage of rows compressed in the partition * 100

NACTIVE Number of active pages in the partition

SYSIBM.SYSCOLSTATS

COLCARDF~ Estimated number of distinct column values in partition

HIGHKEY*~ First 8 bytes of highest value in the column

HIGH2KEY First 8 bytes of second highest value in the column

LOWKEY*~ First 8 bytes of lowest value in the column

LOW2KEY First 8 bytes of second lowest value in the column

SYSIBM.SYSINDEXSTATS

CLUSTER-RATIOF Percentage of rows that are in clustering sequence

CLUSTERED Y if >=95 % of rows in sequence from CLUSTERRATIOFFIRSTKEY-CARDF

Number of distinct values of the first key column

FULLKEY-CARDF

Number of distinct values of the full key

NLEAF Number of active leaf pages

NLEVELS Number of levels in index

KEYCOUNT Number of index keys/entries in index

IOFACTOR Not used

PREFETCH-FACTOR

Not used

SYSIBM.SYSINDEXPART

LIMITKEY~* The upper range value specified when the partitioningindex is created.

~Used by the optimizer if parallelism is considered*Statistics that cannot be updated with UPDATE statement


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Frequency and Correlation Statistics

Frequency statistics are used for reoptimization, dynamic SQL, and predicates with literals on

nonpartitioned tablespaces< INDEX parameter is required for statistics

< Can specify number of values (default of 10)

< > 10 COLVALUE has FREQUENCYF < 9 %

< Uniform distribution is assumed for remaining percentage of rows

Correlation statistics provide the number of distinct values for a column group in a compositeindex

SYSIBM.SYSCOLDIST and SYSIBM.SYSCOLDISTSTATS

COLVALUE One of up to "n" values of the first and additional

(optional) key columns that occur most frequently

FREQUENCYF Percentage of rows that contain the value specified in

COLVALUE * 100 from leaf pages

TYPE 'F' for frequency statistics

'C' for correlation statistics

CARDF Number of distinct values for a column group

COLGROUP-

COLNO

Each SMALLINT array element contains the sequence number

of the column in the row for which statistics arecollected

NUMCOLUMNS Number of columns associated with the statistics

Can update, delete, and insert additional rows< RUNSTATS deletes all inserted rows when executed


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Statistics Updated by RUNSTATS

Used to determine if reorganization is needed and for space management

SYSIBM.SYSTABLEPART

CARDF Number of rows in the table space or partition from

tablespace scan

SPACEF (V7) KB of space as determined by RUNSTATS or STOSPACE

NEARINDREF Number of rows moved to a nearby page (within 2 segments

or 16 pages for a nonsegmented tablespace) due to row

length increase from tablespace scan

FARINDREF Number of rows moved to a faraway page due to row length

increase from tablespace scan

PERCACTIVE Percentage of space occupied by active rows containing

actual data from active tables (not space from deleted

rows). Calculated as active row space bytes /SYSTABLEPART active page bytes.

PERCDROP Percentage of space occupied by rows from dropped tables.

Dropped simple tablespace bytes / SYSTABLEPART active

page bytes.

PAGESAVE Percentage of pages saved in the tablespace or partition

as a result of using ESA compression * 100.

SPACEF (V7) Kilobytes of DASD storage.

DSNUM (V7) Number of data sets for a tablespace or partition.

EXTENTS (V7)Number of data set extents.


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Statistics Updated by RUNSTATS - continued - 1

SYSIBM.SYSINDEXPART

CARDF Number of rows referenced by the index or index partition

from leaf pages

NEAROFFPOSF Number of times the next row was not in sequence of index

but was in a near page from leaf pages. Counter

incremented by 1 if RID >1 and < cutoff pages away from

last RID sequence or in a previous page from the RID.

FAROFFPOSF Number of times the next row was not in sequence of index

but was in a faraway page from leaf pages. Counter

incremented by 1 if RID > cutoff pages away from last RID

sequence.

LEAFDIST 100 times the average number of pages between successive

leaf pages during scan of leaf pages.

SPACEF (V7) KB of space as determined by RUNSTATS or STOSPACE

DSNUM(V7) Number of data sets for index.EXTENTS (V7)Number of extents in index data set.

PSEUDO_DEL_

ENTRIES (V7)

Number of pseudo deleted index entries.

LEAFNEAR V7 Number of leaf pages out of physical position near by.

LEAFFAR (V7)Number of leaf pages out of physical position far off.


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Statistics Updated by RUNSTATS - continued - 2

AVGROWLEN in SYSTABLES is the average row length, useful for:< Variable length rows due to VARCHAR columns prior to V8 and compression< Segmented tablespaces with >1 table< UNLOAD space allocation< REORG and LOAD space allocationS Work data setsS Sort space

PCTPAGES in SYSTABLES and SYSTABSTATS is percentage of total pages that containsrows

< NPAGESF/NACTIVE for nonsegmented tablespace< NPAGESF/(Number of segments * SEGSIZE)


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The RUNSTATS Statement

Update statistics in database DASPJDB tablespace DASPJTSP and all indexes

< Most catalog table columns updated by RUNSTATS contain -1 until it is executed

RUNSTATS TABLESPACE DASPJDB.DASPJTSPINDEX (ALL)SHRLEVEL CHANGEREPORT YES

UPDATE ALL

Statistics collected on all indexes with an index scan after a tablespace scan to collect statisticson data

If only index statistics need to be recalculated,

< A tablespace scan can be avoided by executing RUNSTATS INDEX

RUNSTATS INDEX (AUTHID.SPJX, AUTHID.QTYX)

RUNSTATS can be executed against the catalog tables and indexes< Provides information for the optimizer to choose a good access path for SQL DML

< Statistics are not used for internal manipulation of the catalog tables when objects arecreated, altered, and dropped, plans and packages are bound and freed, privileges are

granted and revoked, and other operations performed on the catalog tables within DB2


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SHRLEVEL Parameter

SHRLEVEL CHANGE allows others to update data

< Uses UR and a read claim- Ignores locks held by programs while collecting statistics

< Collects statistics on data currently being updated

- Does not adversely effect statistics in most cases

- Serializes on mass delete processing

< Good choice

SHRLEVEL REFERENCE allows others to select data while utility is executing (default)< Share lock taken at table/tablespace level

REPORT YES causes statistics to be written to SYSPRINT in addition to updating catalogtables

< Good choice (REPORT NO is the default)


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Parameters Indicate Which Statistics to Update

UPDATE ALL updates statistics for space analysis and those used by the optimizer (default)

UPDATE SPACE updates statistics used for space management analysis< Avoids the possibility of losing current access paths with rebinds

UPDATE ACCESSPATH updates statistics used by the optimizer to determine a good accesspath

< Collection of partial statistics reduces the CPU time

UPDATE NONE can be used with REPORT YES< Can review statistics before having RUNSTATS change statistics, for example

HISTORY parameter causes statistics in the SYSHIST database to be updated in addition to

the catalog tables in the DSNDB06 database< Can be used in conjunction with the ALL, SPACE, and ACCESSPATH (not NONE)

parameters

Catalog tables in the DSNDB06 database are updated when tables in the SYSHIST database areupdated

< There may be an option to update only history statistics in the future


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Update Statistics on a Partition

Can update statistics on a specific partition

RUNSTATS TABLESPACE DASPJDB.DASPJTSPPART 12INDEX (SPJX PART 12)

PART 2 indicates that statistics should be collected for partition 2 of a partitioned tablespace

and the partitioning index

Good choice for specific partitions that are updated frequently< Reduces costs

Advisable to execute RUNSTATS on the entire partitioned tablespace before execution on

individual partitions

Otherwise, tablespace statistics are not updated until statistics have been gathered on allpartitions if part is named

Can name a specific index and its partition

RUNSTATS INDEX (AUTHID.SPJX PART 12)


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Collecting Statistics on Non-Indexed Columns

COLCARDF, HIGH2KEY, and LOW2KEY can be collected on some or all non-indexed

columns (not the default)< Simulation method used

RUNSTATS TABLESPACE DASPJDB.DASPJTSPTABLE (S) COLUMN (ALL)TABLE (SPJ) COLUMN (PN,JN) -- SN not required

SAMPLE 25INDEX (ALL)SHRLEVEL CHANGEUPDATE ALLREPORT YES

If TABLE parameter is specified,< COLUMN (ALL) is the default

< Can name specific columns (10 is the maximum)

Non-indexed column statistics are used for:< Local predicates in determining the join method and the inner and outer table of the join

< Non-leading columns of a composite index when equal predicates are not specified on allcolumns

< More cases expected in future


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Sampling Test Results

Total RUNSTATS CPU time for 15 large tables on a 6-way 600J processor tested by IBM

0 % = No collection of non-indexed column statistics

20 complex SELECT rebound with sampling received the same or better access path except:< 1 had a bad access path with 20 % sampling< 2 had a bad access path with 10 % sampling< 5 had a bad access path with 5 % sampling

Do analyze the access paths your SQL before and after sampling


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Collection of Additional Frequency Statistics

RUNSTATS INDEX (AUTHID.SPJX)

FREQVAL NUMCOLS 1COUNT 15FREQVAL NUMCOLS 2COUNT 25FREQVAL NUMCOLS 3COUNT 35

If FREQVAL is specified,< NUMCOLS must be specified for each group of columns for which frequency statistics are

required and< COUNT indicates the number of frequently occurring values to collect for the group of

columns

Beware of using only< FREQVAL NUMCOLS 3 COUNT 35

< Frequency statistics can be used only if a matching index scan can be used on all 3columns of the composite index

If FREQVAL is not specified,< Frequency statistics are collected on the 1st column of a composite index for the 10 most

frequently occurring values in the column if there is a non-uniform distribution of values

(default)

Also applies to RUNSTATS TABLESPACE

Frequency statistics are particularly important for a skewed distribution of values


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Collection of Correlation Statistics

RUNSTATS TABLESPACE DASPJDB.DASPJTSP

INDEX (ALL) - Can name an index & partitionKEYCARD

Column correlation statistics are written to CARDF in SYSCOLDIST andSYSCOLDISTSTATSif KEYCARD is specified (not the default)

< 1 row for each column group with TYPE='C'

If a composite index has 4 columns,< CARDF contains the cardinality of columns:

- 1 and 2 concatenated- 1, 2, and 3 concatenated

< FULLKEYCARDF has the cardinality of columns 1, 2, 3, and 4 (all columns in compositeindex)

KEYCARD is not needed if< Composite index has


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Report on Correlation Statistics

Summarize the correlation and distribution statistics of indexes on the SPJ table

< WHEN condition needed for each column in the composite index with the most columnsminus 1

SELECT NAME, TYPE, INTEGER(CARDF),CASEWHEN NUMCOLUMNS = 2 THEN

HEX(SUBSTR(COLGROUPCOLNO, 1, 4))WHEN NUMCOLUMNS = 3 THEN

HEX(SUBSTR(COLGROUPCOLNO, 1, 6))ELSE NULLEND AS COLGRPCOLNO,CASEWHEN FREQUENCYF -1 THEN

INTEGER(FLOAT(FREQUENCYF) * 100)ELSE -1

END AS FQY, COLVALUEFROM SYSIBM.SYSCOLDIST

WHERE TBNAME = 'SPJ'AND TBOWNER = 'AUTHID'ORDER BY NAME, TYPE, COLGRPCOLNO,

FQY DESC, COLVALUE;

COLGROUPCOLNO contains an array of SMALLINT columns< Each array element contains the sequence number of the column in the row for which

statistics are collected

NUMCOLUMNS is the number of columns for which the statistics are collected

KEYCARD can result in improved access path selection if the columns of a composite index arecorrelated


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Real-Time Statistics

Statistics are always collected in real time for inserts, updates, and deletes on tablespaces,

partitions, indexes, and logical parts of NPI (V7, APAR PQ48447, PQ48448, and PQ46859)< Written to 2 tables, if they exist, at specified time intervals (30 minutes by default)

Statistics written by LOAD REPLACE and RESUME, REORG, REBUILD INDEX,RUNSTATS UPDATE ALL, COPY, and RECOVER to currency and RECOVER to PIT

< Beware - statistics not written if utility is specified in a utility list

< Specific statistics collected by utilities with various options are detailed in the manuals:< Utility Guide and Reference

< DB2 for z/OS and OS/390 Version 7 Using the Utilities Suite, SG24-6289

Statistics not written if STOP DATABASE(DSNRTSDB) and STOP DB2 MODE(QUIESCE)

Overhead is thought to be less than 1 %< Mostly for recording statistics in 2 tables (statistics are always collected)< Consider placing the objects in a separate buffer pool sized to page fix the objects in

central, data space, or hiperspace storage

Statistics can be analyzed using:

< Control Center with WLM or< DSNACCOR stored procedure using WLM or

< SELECT statements

Useful for analyzing when to execute REORG, RUNSTATS, and COPY utilities< Goal is to have DB2 be self-managed


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-Continue create tableReorgLastTime TIMESTAMP ,ReorgInserts INTEGER ,ReorgDeletes INTEGER ,ReorgUpdates INTEGER ,

ReorgUnClustIns INTEGER ,ReorgDisOrgLob INTEGER ,ReorgMassDelete INTEGER ,ReorgNearIndRef INTEGER ,ReorgFarIndRef INTEGER ,StatsLastTime TIMESTAMP ,StatsInserts INTEGER ,StatsDeletes INTEGER ,StatsUpdates INTEGER ,StatsMassDelete INTEGER ,CopyLastTime TIMESTAMP ,CopyUpdatedPages INTEGER ,CopyChanges INTEGER ,CopyUpdateLRSN CHAR(6) FOR BIT DATA,CopyUpdateTime TIMESTAMP )

IN DSNRTSDB.DSNRTSTS CCSID EBCDIC;

Creation of Real-Time Statistics Objects

DSNTESS in SDSNSAMP contains create statements (objects must be named as indicated)

CREATE DATABASE DSNRTSDB CCSID EBCDIC;

CREATE TABLESPACE DSNRTSTS IN DSNRTSDBCCSID EBCDIC -- requiredLOCKSIZE ROW -- requiredLOCKMAX 0SEGSIZE 32

CLOSE NOUSING STOGROUP SYSDEFLTPRIQTY 1600SECQTY 160;

CREATE TABLE SYSIBM.TABLESPACESTATS(DBNAME CHAR(8) NOT NULL,NAME CHAR(8) NOT NULL,PARTITION INTEGER NOT NULL,

DBID SMALLINT NOT NULL,PSID SMALLINT NOT NULL,UpdateStatsTime TIMESTAMP NOT NULL WITH DEFAULT,TotalRows FLOAT ,Nactive INTEGER ,Space INTEGER ,Extents SMALLINT ,LoadRLastTime TIMESTAMP ,

CREATE UNIQUE INDEX SYSIBM.TABLESPACESTATS_IXON SYSIBM.TABLESPACESTATS(DBID, PSID, PARTITION)CLUSTER CLOSE NO;

Definition of columns can be found in the manualsUtility Guide and Referenceand DB2 for z/OS and

OS/390 Version 7 Using the Utilities Suite, SG24-6289


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CREATE UNIQUE INDEXSYSIBM.INDEXSPACESTATS_IXON SYSIBM.INDEXSPACESTATS(DBID, ISOBID, PSID, PARTITION)CLUSTER CLOSE NO;

Must START DATABASE(DSNRTSDB) aftercreating objects

< DB2 places the database in a stopped state Each sysplex data sharing member collects and

writes statistics

Creation of Real-Time Statistics Objects - continued

CREATE TABLE SYSIBM.INDEXSPACESTATS(DBNAME CHAR(8) NOT NULL,INDEXSPACE CHAR(8) NOT NULL,PARTITION INTEGER NOT NULL,DBID SMALLINT NOT NULL,ISOBID SMALLINT NOT NULL,PSID SMALLINT NOT NULL,UpdateStatsTime TIMESTAMP NOT NULL WITH DEFAULT,TotalEntries FLOAT ,Nlevels SMALLINT ,

Nactive INTEGER ,Space INTEGER ,Extents SMALLINT ,LoadRLastTime TIMESTAMP ,RebuildLastTime TIMESTAMP ,ReorgLastTime TIMESTAMP ,ReorgInserts INTEGER ,ReorgDeletes INTEGER ,

ReorgAppendInsert INTEGER ,ReorgPseudoDeletes INTEGER ,ReorgMassDelete INTEGER ,ReorgLeafNear INTEGER ,ReorgLeafFar INTEGER ,ReorgNumLevels INTEGER ,StatsLastTime TIMESTAMP ,StatsInserts INTEGER ,StatsDeletes INTEGER ,StatsMassDelete INTEGER ,CopyLastTime TIMESTAMP ,CopyUpdatedPages INTEGER ,CopyChanges INTEGER ,CopyUpdateLRSN CHAR(6) FOR BIT DATA,CopyUpdateTime TIMESTAMP )IN DSNRTSDB.DSNRTSTS CCSID EBCDIC;


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Control Center

Control Center can be used to set thresholds

Calls DSNACCOR stored procedure to report on recommendations for execution of utilities

Calls DSNUTILS stored procedure to execute utilities


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Degree of Checking and Scope

DSNACCOR degree of check can be:

0 = No Additional checking, base function only1 = Do not include any deleted objects in the DSNACCOR result set2 = Record table space names related to index spaces

4 = Use the exception table ( if one exists )

8 = Return status on restricted objects16 = Include any deleted objects in the result set but mark "status" as orphaned

32 = Scale up to table space recommendation on reorg if appropriate

Degree of check option is set to the sum of the categories needed< If you would like category 1, 2, and 4,S Use 7 which is the sum of 1, 2, and 4(default)

Scope of objects can be controlled with a WHERE clause (


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--Continue call parameters:RRIAPPENDINSERTPCT :RRIAPPENDINSERTPCT-IND,:RRIPSEUDODELETEPCT :RRIPSEUDODELETEPCT-IND,:RRIMASSDELLIMIT :RRIMASSDELLIMIT-IND,:RRILEAFLIMIT :RRILEAFLIMIT-IND,:RRINUMLEVELSLIMIT :RRINUMLEVELSLIMIT-IND,:SRTINSDELUPDPCT :SRTINSDELUPDPCT-IND,

:SRTINSDELUPDABS :SRTINSDELUPDABS-IND,:SRTMASSDELLIMIT :SRTMASSDELLIMIT-IND,:SRIINSDELUPDPCT :SRIINSDELUPDPCT-IND,:SRIINSDELUPDABS :SRIINSDELUPDABS-IND,:SRIMASSDELLIMIT :SRIMASSDELLIMIT-IND,:EXTENTLIMIT :EXTENTLIMIT-IND,:LASTSTATEMENT :LASTSTATEMENT-IND,:RETURNCODE :RETURNCODE-IND,

:ERRORMSG :ERRORMSG-IND,:IFCARETCODE :IFCARETCODE-IND,:IFCARESCODE :IFCARESCODE-IND,:XSBYTES :XSBYTES-IND)END-EXEC.

Calling DSNACCOR Stored Procedure

Recommendations can be generated by calling stored procedure DSNACCOR in SDSNSAMP

EXEC SQLCALL SYSPROC.DSNACCOR(:QUERYTYPE :QUERYTYPE-IND,:OBJECTTYPE :OBJECTTYPE-IND,:ICTYPE :ICTYPE-IND,:STATSSCHEMA :STATSSCHEMA-IND,:CATLGSCHEMA :CATLGSCHEMA-IND,:LOCALSCHEMA :LOCALSCHEMA-IND,

:CHKLVL :CHKLVL-IND,:CRITERIA :CRITERIA-IND,:CRUPDATEDPAGESPCT :CRUPDATEDPAGESPCT-IND,:CRCHANGESPCT :CRCHANGESPCT-IND,:CRDAYSNCLASTCOPY :CRDAYSNCLASTCOPY-IND,:ICRUPDATEDPAGESPCT :ICRUPDATEDPAGESPCT-IND,:CRINDEXSIZE :CRINDEXSIZE-IND,:RRTINSDELUPDPCT :RRTINSDELUPDPCT-IND,

:RRTUNCLUSTINSPCT :RRTUNCLUSTINSPCT-IND,:RRTDISORGLOBPCT :RRTDISORGLOBPCT-IND,:RRTMASSDELLIMIT :RRTMASSDELLIMIT-IND,:RRTINDREFLIMIT :RRTINDREFLIMIT-IND,:RRIINSERTDELETEPCT :RRIINSERTDELETEPCT-IND,

DB2 for z/OS and OS/390Administration Guide, SC26-9931, manual contains: OFFPOSLIMIT (10 % default) assuming that limit parameter is specified,

< A reorganization of the tablespace or named partitions are performed along with the

indexes on the objects

NEAROFFPOSF is the number of times it is necessary to access a different, "near-off" pagewhen processing rows in sequence according to the index

< Segmented tablespace row is near-off position if the difference between the 2 page IDs is>= 2 and < SEGSIZE * 2 (16 rather than SEGSIZE * 2 is used for nonsegmented

tablespaces)

FAROFFPOSF is the number of times it is necessary to access a different, "far-off" page whenprocessing rows in sequence according to the index

< Segmented tablespace row is far-off position if the 2 page IDs differ by SEGSIZE * 2 or

more (16 rather than SEGSIZE * 2 is used for nonsegmented tablespaces)

0AND ((NEARINDREF+FARINDREF) * 100 / CARDF) > 0;

If REORG finds that (NEARINDREF + FARINDREF) * 100 / CARDF > INDREFLIMIT (10% default) (V6) assuming that limit parameter is specified,

10 % of an index is occupied by pseudo deleted RIDs,< Consider reorganizing or rebuilding the index

SELECT IXCREATOR, IXNAME, PSEUDO_DEL_ENTRIES, PGREATER10FROM SYSIBM.SYSINDEXPART

WHERE (PSEUDO_DEL_ENTRIES * 100 / CARDF) > 10 AS PGREATER10

Many more parameters discussed in the remainder of section that you will want to include inthe REORG TABLESPACE and REORG INDEX statements

Determining Free Space Available/Unavailable


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Determining Free Space Available/Unavailable

Determine the amount of free space currently on pages for tablespaces in the DASPJDB database

SELECT TSNAME, DBNAME, PERCACTIVEFROM SYSIBM.SYSTABLEPARTWHERE DBNAME = 'DASPJDB';

If PERCACTIVE > 95, some of 5 % free space (default) has been used 0,< Space from a dropped table is not reusable

SELECT TSNAME, DBNAME, PERCDROPFROM SYSIBM.SYSTABLEPARTWHERE PERCDROP > 0;

Alternative is to use a segmented tablespace=

(SELECT COALESCE(MAX(STATSTIME),

'0001-01-01.00.00.00.000000')FROM SYSIBM.SYSTABLEPART)ORDER BY EXTENTS;

Can determine number of pseudo deleted RIDs for indexesSELECT IXNAME, EXTENTS, DSNUM, SPACEF, PSEUDO_DEL_ENTRIES,STATSTIMEFROM SYSIBM.SYSINDEXPARTWHERE IXCREATOR = 'MKTGWX'AND STATSTIME >=(SELECT COALESCE(MAX(STATSTIME),

'0001-01-01.00.00.00.000000')FROM SYSIBM.SYSINDEXPART)ORDER BY EXTENTS;

Alternatives to Determine Secondary Extents


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LISTCAT (AMS (Access Method Services)) command can be used to determine secondaryextents from the ICF catalog, for example

LISTCAT LEVEL(DSNP.DSNDBD.DSNDB07.*) ALL

ISPF 3.4 can be used, for example< Dsname Level . . . DSNP.DSNDBD.DSNDB07.* with option 2

S Gives the space allocated for work tablespaces

< SORT XT lists the data sets in multiple extents first

If real-time statistics are recorded,< SYSIBM.TABLESPACESTATS contains space information

for DSNDB07 and TEMP tablespaces in columns:

S

NACTIVE, SPACE, EXTENTS

Cannot use catalog tables to analyze space for DSNDB07< RUNSTATS does not collect statistics on DSNDB07

Frequently used for partitioned tablespaces

Documents

Runstats and Reorg