Oracle提供了索引監(jiān)控特性來(lái)判斷索引是否被使用。在Oracle 10g中，收集統(tǒng)計(jì)信息會(huì)使得索引被監(jiān)控，在Oracle 11g中該現(xiàn)象不復(fù)存在。盡管如此，該方式僅提供的是索引是否被使用。索引被使用的頻率未能得以體現(xiàn)。下面的腳本將得到索引的使用率，可以很好的度量索引的使用情況以及根據(jù)這個(gè)值來(lái)判斷當(dāng)前的這些索引是否可以被移除或改進(jìn)。
1、索引使用頻率報(bào)告
--運(yùn)行環(huán)境
SQL> select * from v$version where rownum2;
BANNER
----------------------------------------------------------------
Oracle Database 10g Release 10.2.0.3.0 - 64bit Production
--獲得當(dāng)前數(shù)據(jù)庫(kù)索引的使用頻率
SQL> @idx_usage_detail.sql
Enter value for 1: GO_ADMIN
Enter value for 2: 100
Index
Table name Index name Index type Size MB Index operation Executions
------------------------------ ------------------------------ ------------ ----------- --------------------- ----------
ACC_POS_CASH_PL_TBL_ARC PK_ACC_POS_CASH_PL_ARCH_TBL NORMAL 3,328.00 RANGE SCAN 99
SAMPLE FAST FULL SCAN 8
UNIQUE SCAN 3
SKIP SCAN 2
****************************** ****************************** ************ ----------- ----------
sum 13,312.00 112
ACC_POS_CASH_TBL_ARC PK_ACC_POS_CASH_ARCH_TBL NORMAL 2,560.00 RANGE SCAN 168
UNIQUE SCAN 14
SAMPLE FAST FULL SCAN 12
SKIP SCAN 1
****************************** ****************************** ************ ----------- ----------
sum 10,240.00 195
ACC_POS_HIST_TBL ACC_HIST_TRANS_DATE_IDX NORMAL 384.00 RANGE SCAN 917
SKIP SCAN 210
SAMPLE FAST FULL SCAN 4
FAST FULL SCAN 1
PK_ACC_POS_HIST_TBL NORMAL 192.00 UNIQUE SCAN 7
SAMPLE FAST FULL SCAN 3
TRANS_NUM_IDX NORMAL 232.00 RANGE SCAN 41
SAMPLE FAST FULL SCAN 3
FAST FULL SCAN 1
****************************** ****************************** ************ ----------- ----------
sum 2,616.00 1,187
ACC_POS_INT_TBL ACC_POS_INT_10DIG_IDX FUNCTION- 2,622.00 RANGE SCAN 59
BASED NORMAL
SAMPLE FAST FULL SCAN 4
FAST FULL SCAN 2
PK_ACC_POS_INT_TBL NORMAL 2,496.00 RANGE SCAN 65
FAST FULL SCAN 53
UNIQUE SCAN 14
SKIP SCAN 13
SAMPLE FAST FULL SCAN 1
****************************** ****************************** ************ ----------- ----------
sum 20,346.00 211
ACC_POS_STOCK_TBL_ARC PK_ACC_POS_STOCK_ARCH_TBL NORMAL 18,977.00 RANGE SCAN 177
SAMPLE FAST FULL SCAN 10
UNIQUE SCAN 4
SKIP SCAN 3
****************************** ****************************** ************ ----------- ----------
sum 75,908.00 194
STK_TBL_ARC PK_STK_ARCH_TBL NORMAL 920.00 RANGE SCAN 126
UNIQUE SCAN 38
SKIP SCAN 17
SAMPLE FAST FULL SCAN 2
****************************** ****************************** ************ ----------- ----------
sum 3,680.00 183
STK_TBL_LOG PK_STK_TBL_LOG NORMAL 480.00 UNIQUE SCAN 56
****************************** ****************************** ************ ----------- ----------
sum 480.00 56
TRADE_BROKER_CHRG_TBL_ARC PK_TRADE_BROKER_CHRG_TBL_ARC NORMAL 128.00 - 0
UNI_TDBK_CHRG_ARC NORMAL 104.00 RANGE SCAN 283
****************************** ****************************** ************ ----------- ----------
sum 232.00 283
TRADE_BROKER_JOURNAL_TBL_ARC IDX_TDBK_JRNL_ARC_ENTRY_DT NORMAL 168.00 - 0
IDX_TDBK_JRNL_ARC_INSTRU_ID NORMAL 144.00 FULL SCAN 1
IDX_TDBK_JRNL_ARC_STOCK_CD NORMAL 144.00 FULL SCAN 1
IDX_TDBK_JRNL_ARC_TRADED_PRICE NORMAL 144.00 FULL SCAN 1
PK_TRADE_BROKER_JOURNAL_ARC NORMAL 200.00 - 0
****************************** ****************************** ************ ----------- ----------
sum 800.00 3
TRADE_CLIENT_CHRG_TBL_ARC IDX_TDCL_CHRG_ARC_GRP_REF_ID NORMAL 704.00 RANGE SCAN 3,537
PK_TRADE_CLIENT_CHRG_TBL_ARC NORMAL 1,539.00 RANGE SCAN 24
SAMPLE FAST FULL SCAN 2
UNI_TDCL_CHRG_ARC NORMAL 1,216.00 RANGE SCAN 1,103
FAST FULL SCAN 3
SAMPLE FAST FULL SCAN 2
****************************** ****************************** ************ ----------- ----------
sum 7,430.00 4,671
TRADE_CLIENT_DTL_TBL_ARC IDX_TDCL_DTL_ARC_ACTION_N_STUS NORMAL 312.00 - 0
IDX_TDCL_DTL_ARC_ACT_TD_PRICE NORMAL 184.00 FULL SCAN 1
IDX_TDCL_DTL_ARC_REF_ID NORMAL 344.00 RANGE SCAN 4,623
FAST FULL SCAN 1
FULL SCAN 1
IDX_TDCL_DTL_ARC_TRADED_PRICE NORMAL 184.00 - 0
PK_TRADE_CLIENT_DTL_TBL_ARC NORMAL 432.00 - 0
UNI_TDCL_DTL_ARC_TRADE_DTL_ID NORMAL 272.00 - 0
****************************** ****************************** ************ ----------- ----------
sum 2,416.00 4,626
TRADE_CLIENT_TBL_ARC IDX_TDCL_ARC_ACC_NUM NORMAL 152.00 RANGE SCAN 534
IDX_TDCL_ARC_GRP_REF_ID NORMAL 120.00 RANGE SCAN 550
FAST FULL SCAN 1
IDX_TDCL_ARC_INPUT_DATE NORMAL 120.00 RANGE SCAN 7,231
IDX_TDCL_ARC_PL_STK NORMAL 144.00 SKIP SCAN 156
RANGE SCAN 3
FULL SCAN 1
IDX_TDCL_ARC_TRADE_DATE NORMAL 120.00 RANGE SCAN 12,778
PK_TRADE_CLIENT_TBL_ARC NORMAL 160.00 RANGE SCAN 37
UNI_TDCL_ARC_REF_ID NORMAL 112.00 UNIQUE SCAN 157
FAST FULL SCAN 8
SAMPLE FAST FULL SCAN 1
****************************** ****************************** ************ ----------- ----------
sum 1,560.00 21,457
--Author : Robinson
--Blog : http://blog.csdn.net/robinson_0612
"Showed only indexes in GO_ADMIN schema whose size > 100 MB in period:"
30.01.2013-07.04.2013
2、結(jié)果分析與建議
a、上面的結(jié)果列出了當(dāng)前數(shù)據(jù)庫(kù)中schema為GOEX_ADMIN且索引大小大于100MB的索引的使用頻率。
b、由于當(dāng)前的數(shù)據(jù)庫(kù)為標(biāo)準(zhǔn)版，沒(méi)有分區(qū)表功能，所以可以看到很多arc結(jié)尾的表，且索引很大，如ACC_POS_STOCK_TBL_ARC上索引達(dá)到19G。
c、表ACC_POS_CASH_PL_TBL_ARC上的主鍵PK_ACC_POS_CASH_PL_ARCH_TBL上范圍掃描最多，總計(jì)被使用次數(shù)為112次。
d、對(duì)于上述列出的被使用的次數(shù)為0的那些索引，應(yīng)考慮索引的設(shè)置是否合理。
e、過(guò)大的索引應(yīng)考慮能否使用索引壓縮。
f、最后列出的是報(bào)告的schema名稱以及索引大小的過(guò)濾條件、索引被收集的日期。注，索引列的大小sum求和有些不準(zhǔn)確。
3、獲得索引使用頻率腳本
--該腳本作者為Damir Vadas，感謝Damir Vadas的貢獻(xiàn)
robin@SZDB:~/dba_scripts/custom/sql> more idx_usage_detail.sql
/* ---------------------------------------------------------------------------
CR/TR# :
Purpose : Shows index usage by execution (find problematic indexes)
Date : 22.01.2008.
Author : Damir Vadas, damir.vadas@gmail.com
Remarks : run as privileged user
Must have AWR run because sql joins data from there
works on 10g >
@index_usage SCHEMA MIN_INDEX_SIZE
Changes (DD.MM.YYYY, Name, CR/TR#):
25.11.2010, Damir Vadas
added index size as parameter
30.11.2010, Damir Vadas
fixed bug in query
--------------------------------------------------------------------------- */
set linesize 140
set pagesize 160
clear breaks
clear computes
break on TABLE_NAME skip 2 ON INDEX_NAME ON INDEX_TYPE ON MB
compute sum of NR_EXEC on TABLE_NAME SKIP 2
compute sum of MB on TABLE_NAME SKIP 2
SET TIMI OFF
set linesize 140
set pagesize 10000
set verify off
col OWNER noprint
col TABLE_NAME for a30 heading 'Table name'
col INDEX_NAME for a30 heading 'Index name'
col INDEX_TYPE for a15 heading 'Index type'
col INDEX_OPERATION for a21 Heading 'Index operation'
col NR_EXEC for 9G999G990 heading 'Executions'
col MB for 999G990D90 Heading 'Index|Size MB' justify right
WITH Q AS (
SELECT
S.OWNER A_OWNER,
TABLE_NAME A_TABLE_NAME,
INDEX_NAME A_INDEX_NAME,
INDEX_TYPE A_INDEX_TYPE,
SUM(S.bytes) / 1048576 A_MB
FROM DBA_SEGMENTS S,
DBA_INDEXES I
WHERE S.OWNER = '1'
AND I.OWNER = '1'
AND INDEX_NAME = SEGMENT_NAME
GROUP BY S.OWNER, TABLE_NAME, INDEX_NAME, INDEX_TYPE
HAVING SUM(S.BYTES) > 1048576 * 2
)
SELECT /*+ NO_QUERY_TRANSFORMATION(S) */
A_OWNER OWNER,
A_TABLE_NAME TABLE_NAME,
A_INDEX_NAME INDEX_NAME,
A_INDEX_TYPE INDEX_TYPE,
A_MB MB,
DECODE (OPTIONS, null, ' -',OPTIONS) INDEX_OPERATION,
COUNT(OPERATION) NR_EXEC
FROM Q,
DBA_HIST_SQL_PLAN d
WHERE
D.OBJECT_OWNER(+)= q.A_OWNER AND
D.OBJECT_NAME(+) = q.A_INDEX_NAME
GROUP BY
A_OWNER,
A_TABLE_NAME,
A_INDEX_NAME,
A_INDEX_TYPE,
A_MB,
DECODE (OPTIONS, null, ' -',OPTIONS)
ORDER BY
A_OWNER,
A_TABLE_NAME,
A_INDEX_NAME,
A_INDEX_TYPE,
A_MB DESC,
NR_EXEC DESC
;
PROMPT "Showed only indexes in 1 schema whose size > 2 MB in period:"
SET HEAD OFF;
select to_char (min(BEGIN_INTERVAL_TIME), 'DD.MM.YYYY')
|| '-' ||
to_char (max(END_INTERVAL_TIME), 'DD.MM.YYYY')
from dba_hist_snapshot;
SET HEAD ON
SET TIMI ON
4、補(bǔ)充說(shuō)明
腳本使用了2個(gè)替代變量，一個(gè)是schema，一個(gè)是索引的大小。缺省情況下，對(duì)于那些較小的索引以及僅僅運(yùn)行一至兩次的sql語(yǔ)句的歷史執(zhí)行計(jì)劃不會(huì)被收集到DBA_HIST_SQL_PLAN。因此執(zhí)行腳本時(shí)索引大小輸入的建議值是100。如果需要收集所有的歷史sql執(zhí)行計(jì)劃來(lái)判斷索引是否被使用，需要修改statistics_level為all或者修改snapshot的收集策略。收集策略對(duì)系統(tǒng)性能有一定的影響，以及耗用大量磁盤(pán)空間，因此Prod環(huán)境應(yīng)慎用(UAT和DEV則無(wú)妨)。
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