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。
robin@SZDB:~/dba_scripts/custom/bin> more rebuild_unbalanced_indices.sh
# +-------------------------------------------------------+
# + Rebulid unblanced indices |
# + Author : Leshami |
# + Parameter : No |
# + Blog : http://blog.csdn.net/leshami |
# +-------------------------------------------------------+
#!/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` !!!" ${DBA} <${LOG}
else
mail -s "Failed rebuilding indices on `hostname` !!!" ${DBA} <${LOG}
fi
# ------------------------------------------------
# Removing files older than $RETENTION parameter
# ------------------------------------------------
find ${LOG_DIR} -name "rebuild_unb*" -mtime +$RETENTION -exec rm {} \;
exit
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
'alte