查看執(zhí)行計劃：

db2expln:

db2expln -d dbname -c pkgOwner -p pkgNmae -o expln.out

dynexpln:

dynexpln -d eos -q 'select * from eosmenu' -g -t

dynexpln -d eos -f query.sql -o out.txt

更新統(tǒng)計信息：

runstats:

db2 runstats on table songxn.eosmenu and indexs songxn.ix1,songxn.ix2 allow read access

db2 runstats on table songxn.eosmenu with distribution and detailed index all

調整優(yōu)化等級：

(0,1,2,3,5,7,9)：

更改DFT_QUERYOPT(db cfg)， 默認為5

SQL:set current query optimization = 3

索引：

建立索引：

create unique index ind1 on vicky.staff ( dept, lastname )

create unique index ind2 on vicky.emplyee ( empno ) include ( lastname, salary)

include中的字段不列入排序范圍

叢集索引：

記錄與索引的順序一致

cretae index ind3 on vicky.staff ( dept ) CLUSTER

SCAN MODE:

Index Scan,Full Index Scan(Index only Access),Relation Scan

查詢索引：

select indname from syscat.indexes where tabname='customer'

索引建議器：

db2advis -d dbname -i query.sql | -s 'sql stmt' -o advis.out

在數(shù)據(jù)頁中預留空間：

alter table vicky.staff PCTFREE 30（預留30％）

load from staff.ixf of ixf modified by pagefreespace=30 replace into vicky.staff

緩沖池與IO

默認為IBMDEFAULTBP

新建緩沖池：

db2 create bufferpool bpname size 1000 pagesize 4k

alter tablespace tbname bufferpool bpname

當臟頁超過CHNGPGS_THRESH(%,db cfg)時，緩沖池將被清空并寫回

延展緩沖池:

ESTORE_SEG_SZ& NUM_ESTORE_SEGS(db cfg)

db2 alter bufferpool ibmdefaultbp [ not ] extended storage

I/O SERVER:

NUM_IOSERVERS(db cfg):一般為磁盤數(shù)+2

數(shù)據(jù)重整:

REORGCHK:

db2 reorgchk update statistics on table all 該語句也用來對所有表做RUNSTATS

db2 reorgchk current statistics on table vicky.staff

table statistics：

CARD:記錄筆數(shù)

OV(ERFLOW):overflow的記錄數(shù)

NP(AGES):含有記錄的頁數(shù)

FP(AGES):表格占用的總頁數(shù)

TSIZE(Bytes):表格大小

index statistics:

LEAF:leaf page數(shù)

ELEAF:空葉數(shù)

NDEL:被刪除的RID數(shù)

LVLS:索引層級數(shù)

ISIZE:索引平均長度

KEYS:不同的索引值的個數(shù)

表格重整：

db2 reorg table vicky.staff index ind1 use tempspace2 indexscan

索引重整：

db2 reorg indexes all for table vicky.staff _options_

options:allow read|write|no access, cleanup only pages|all（不重建索引結構，只回收空索引頁）

聯(lián)機表格重整(V8+)：

db2 reorg table vicky.staff index vicky.ind2 inplace allow write access

db2 reorg table vicky.staff index vicky.ind2 inplace pause|resume

db2 list history reorg all for dbname

MQT

MQT:

建立MQT:

CREATE TABLE vicky.mqt1 AS

( SELECT name, location, salary

FROM vicky.staff, vicky.org

WHERE staff.dept=org.deptnumb AND salary>20000

) DATA INITIALLY DEFERRED REFRESH DEFERRED|IMMEDIATE

ENABLE|DISABLE QUERY OPTIMIZATION

REFRESH TABLE vicky.mqt1

利用MQT:

RUNSTATS ON TABLE vicky.mqt1

UPDATE DB CFG FOR sample USING DFT_REFRESH_AGE ANY

并行處理

設置并行處理：

UPDATE DBM CFG USING INTRA_PARALLEL YES

UPDATE DB CFG FOR EOS USING DFT_DEGREE ANY

并行處理上限：

應用級：

SET RUNTIME DEGREE FOR ( 25 ) TO 4

SET RUNTIME DEGREE FOR ALL TO 6

實例級：

UPDATE DBM CFG USING MAX_QUERYDEGREE 6

MDC表:

CREATE TABLE vicky.sales

( YearAndMonth CHAR(4),

Region CHAR(20),

Product CHAR(2),

Sales BIGINT

) ORGANIZE BY DIMENSIONS ( YearAndMonth, Region )

CREATE TABLE vicky.table1

( col1 CHAR(10),

col2 CHAR(10),

col3 CHAR(10),

col4 INTEGER,

col5 DECIMAL(10,2),

) ORGANIZE BY DIMENSIONS ( col1, ( col2, col3 ),col4 )