索引是提高数据库查询性能的有力武器。没有索引，就好比图书馆没有图书标签一样，找一本书自己想要的书比登天还难。然而索引在使用的过程中，尤其是在批量的DML的情形下会产生相应的碎片，以及B树高度会发生相应变化，因此可以对这些变化较大的索引进行重构以提高性能。N久以前Oracle建议我们定期重建那些高度为4，已删除的索引条目至少占有现有索引条目总数的20%的这些表上的索引。但Oracle现在强烈建议不要定期重建索引。具体可以参考文章：Oracle 重建索引的必要性。尽管如此重建索引还是有必要的，只是不建议定期。本文给出了重建索引的脚本供大家参考。

1、重建索引shell脚本

robin@SZDB:~/dba_scripts/custom/bin> more rebuild_unbalanced_indices.sh

# +-------------------------------------------------------+

# + Rebulid unblanced indices |

# + Author : Leshami |

# + Parameter : No |

# +-------------------------------------------------------+

#!/bin/bash

# --------------------

# Define variable

# --------------------

if [ -f ~/.bash_profile ]; then

. ~/.bash_profile

fi

DT=`date +%Y%m%d`; export DT

RETENTION=1

LOG_DIR=/tmp

LOG=${LOG_DIR}/rebuild_unbalanced_indices_${DT}.log

DBA=Leshami@12306.cn

# ------------------------------------

# Loop all instance in current server

# -------------------------------------

echo "Current date and time is : `/bin/date`">>${LOG}

for db in `ps -ef | grep pmon | grep -v grep |grep -v asm |awk '{print $8}'|cut -c 10-`

do

echo "$db"

export ORACLE_SID=$db

echo "Current DB is $db" >>${LOG}

echo "===============================================">>${LOG}

$ORACLE_HOME/bin/sqlplus -S /nolog @/users/robin/dba_scripts/custom/sql/rebuild_unbalanced_indices.sql>>${LOG}

done;

echo "End of rebuilding index for all instance at : `/bin/date`">>${LOG}

# -------------------------------------

# Check log file

# -------------------------------------

status=`grep "ORA-" ${LOG}`

if [ -z $status ];then

mail -s "Succeeded rebuilding indices on `hostname` !!!" ${DBA}

else

mail -s "Failed rebuilding indices on `hostname` !!!" ${DBA}

fi

# ------------------------------------------------

# Removing files older than $RETENTION parameter

# ------------------------------------------------

find ${LOG_DIR} -name "rebuild_unb*" -mtime +$RETENTION -exec rm {} \;

exit

2、重建索引调用的SQL脚本

robin@SZDB:~/dba_scripts/custom/sql> more rebuild_unbalanced_indices.sql

conn / as sysdba

set serveroutput on;

DECLARE

resource_busy EXCEPTION;

PRAGMA EXCEPTION_INIT (resource_busy, -54);

c_max_trial CONSTANT PLS_INTEGER := 10;

c_trial_interval CONSTANT PLS_INTEGER := 1;

pmaxheight CONSTANT INTEGER := 3;

pmaxleafsdeleted CONSTANT INTEGER := 20;

CURSOR csrindexstats

IS

SELECT NAME,

height,

lf_rows AS leafrows,

del_lf_rows AS leafrowsdeleted

FROM index_stats;

vindexstats csrindexstats%ROWTYPE;

CURSOR csrglobalindexes

IS

SELECT owner,index_name, tablespace_name

FROM dba_indexes

WHERE partitioned = 'NO'

AND owner IN ('GX_ADMIN');

CURSOR csrlocalindexes

IS

SELECT index_owner,index_name, partition_name, tablespace_name

FROM dba_ind_partitions

WHERE status = 'USABLE'

AND index_owner IN ('GX_ADMIN');

trial PLS_INTEGER;

vcount INTEGER := 0;

BEGIN

trial := 0;

/* Global indexes */

FOR vindexrec IN csrglobalindexes

LOOP

EXECUTE IMMEDIATE

'analyze index ' || vindexrec.owner ||'.'|| vindexrec.index_name || ' validate structure';

OPEN csrindexstats;

FETCH csrindexstats INTO vindexstats;

IF csrindexstats%FOUND

THEN

IF (vindexstats.height > pmaxheight)

OR ( vindexstats.leafrows > 0

AND vindexstats.leafrowsdeleted > 0

AND (vindexstats.leafrowsdeleted * 100 / vindexstats.leafrows) >

pmaxleafsdeleted)

THEN

vcount := vcount + 1;

DBMS_OUTPUT.PUT_LINE (

'Rebuilding index ' || vindexrec.owner ||'.'|| vindexrec.index_name || '...');

<>

BEGIN

EXECUTE IMMEDIATE

'alter index '

|| vindexrec.owner ||'.'

|| vindexrec.index_name

|| ' rebuild'

|| ' parallel nologging compute statistics'

|| ' tablespace '

|| vindexrec.tablespace_name;

EXCEPTION

WHEN resource_busy OR TIMEOUT_ON_RESOURCE

THEN

DBMS_OUTPUT.PUT_LINE (

'alter index - busy and wait for 1 sec');

DBMS_LOCK.sleep (c_trial_interval);

IF trial <= c_max_trial

THEN

GOTO alter_index;

ELSE

DBMS_OUTPUT.PUT_LINE (

'alter index busy and waited - quit after '

|| TO_CHAR (c_max_trial)

|| ' trials');

RAISE;

END IF;

WHEN OTHERS

THEN

DBMS_OUTPUT.PUT_LINE ('alter index err ' || SQLERRM);

RAISE;

END;

END IF;

END IF;

CLOSE csrindexstats;

END LOOP;

DBMS_OUTPUT.PUT_LINE ('Global indices rebuilt: ' || TO_CHAR (vcount));

vcount := 0;

trial := 0;

/* Local indexes */

FOR vindexrec IN csrlocalindexes

LOOP

EXECUTE IMMEDIATE

'analyze index '

|| vindexrec.index_owner||'.'

|| vindexrec.index_name

|| ' partition ('

|| vindexrec.partition_name

|| ') validate structure';

OPEN csrindexstats;

FETCH csrindexstats INTO vindexstats;

IF csrindexstats%FOUND

THEN

IF (vindexstats.height > pmaxheight)

OR ( vindexstats.leafrows > 0

AND vindexstats.leafrowsdeleted > 0

AND (vindexstats.leafrowsdeleted * 100 / vindexstats.leafrows) >

pmaxleafsdeleted)

THEN

vcount := vcount + 1;

DBMS_OUTPUT.PUT_LINE (

'Rebuilding index ' || vindexrec.index_owner||'.'|| vindexrec.index_name || '...');

<>

BEGIN

EXECUTE IMMEDIATE

'alter index '

|| vindexrec.index_owner||'.'

|| vindexrec.index_name

|| ' rebuild'

|| ' partition '

|| vindexrec.partition_name

|| ' parallel nologging compute statistics'

|| ' tablespace '

|| vindexrec.tablespace_name;

EXCEPTION

WHEN resource_busy OR TIMEOUT_ON_RESOURCE

THEN

DBMS_OUTPUT.PUT_LINE (

'alter partitioned index - busy and wait for 1 sec');

DBMS_LOCK.sleep (c_trial_interval);

IF trial <= c_max_trial

THEN

GOTO alter_partitioned_index;

ELSE

DBMS_OUTPUT.PUT_LINE (

'alter partitioned index busy and waited - quit after '

|| TO_CHAR (c_max_trial)

|| ' trials');

RAISE;

END IF;

WHEN OTHERS

THEN

DBMS_OUTPUT.PUT_LINE (

'alter partitioned index err ' || SQLERRM);

RAISE;

END;

END IF;

END IF;

CLOSE csrindexstats;

END LOOP;

DBMS_OUTPUT.PUT_LINE ('Local indices rebuilt: ' || TO_CHAR (vcount));

END;

/

exit;

3、输入日志样本

Current date and time is : Sun Apr 20 02:00:02 HKT 2014

Current DB is SYBO2 ===============================================

Rebuilding index GX_ADMIN.SYN_OUT_DATA_TBL_PK...

Rebuilding index GX_ADMIN.IDX_TDBK_SPLNK_PARENT_REF...

Rebuilding index GX_ADMIN.IDX_TDBK_SPLNK_CHILD_REF...

Rebuilding index GX_ADMIN.PK_TRADE_BROKER_TBL...

Rebuilding index GX_ADMIN.IDX_TDBK_INPUT_DATE...

................

4、后记

a、如果同一台服务器上有多个实例，且每个实例有相同的schema，此脚本会轮巡所有实例并根据analyze结果来rebuild。

a、大家应根据需要作相应调整，如脚本的路径信息等。

b、需要修改相应的schema name。

d、可根据系统环境调整相应的并行度。