Oracle提供了索引監(jiān)控特性來判斷索引是否被使用。在Oracle 10g中，收集統(tǒng)計(jì)信息會使得索引被監(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)這個值來判斷當(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

?123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136 --運(yùn)行環(huán)境 SQL> select * from v$version where rownum<2; BANNER ---------------------------------------------------------------- Oracle Database 10g Release 10.2.0.3.0 - 64bit Production --獲得當(dāng)前數(shù)據(jù)庫索引的使用頻率 SQL> @idx_usage_detail.sql Enter value for 1: GO_ADMIN Enter value for 2: 100 IndexTable 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)庫為標(biāo)準(zhǔn)版，沒有分區(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

?123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100 --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 OFFset linesize 140 set pagesize 10000 set verify offcol 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 ONSET TIMI ON

4、補(bǔ)充說明

腳本使用了2個替代變量，一個是schema，一個是索引的大小。缺省情況下，對于那些較小的索引以及僅僅運(yùn)行一至兩次的sql語句的歷史執(zhí)行計(jì)劃不會被收集到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。收集策略對系統(tǒng)性能有一定的影響，以及耗用大量磁盤空間，因此Prod環(huán)境應(yīng)慎用(UAT和DEV則無妨)。

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