性能调优（不能重启数据库）
索引
资源管理器
性能优化
统计分析
SQL性能分析
SPM (SQL执行计划管理)
堆表 ：数据存储无序
位图索引 ：适合字段重复值高的，数据仓库环境下（适合OLAP/DSS环境），存储占用空间少, DML成本高, WHERE中与或操作效率高
eg :
select count(*) from customers where m_status = married and region in (‘central’, ‘west’);
eg :
su -oracle
sqlplus / as sysdba
set linesize 120
set pagesize 20
line on
timing on
sqlprompt ‘[email protected]_connect_identifier’
start up
alter user scott identified by tiger unlock;
conn scott/tiger
create table t1 (id number, color varchar2, pty number);
begin for i in 1..50000 loop insert into t1 values(1, blue’, 1000); end loop; commt; end; /
select count(*) from t1;
update t1 set color=‘red’ where id < 20001;
update t1 set color=‘green’ where id > 40000;
commit;
select distinct color from t1;
!clear
create tablespace indx datafile ‘/u01/app/oracle/prod/indx01.dbf’ size 100m;
create indext1_color_ind on t1(color) tablespace indx;
analyze table t1 compute statistics; (表分析)
analyze index t1_color_ind compute statistics;
select a.table_name, a.index_name, a.index_type, a.leef_blocks, b.height from user_indexes a.index_stats b where a.index_mane=b.index_name and a.index_name=’T1_COLOR_IND’;
col table_name for a10
col index_name for a10
@?sqlplus/
conn scott/tiger
set autrace trace
select count(*) from t1 where color=‘blue’;
set auto trace off
select * from t1 where id<10;
drop index t1_color_indx;
create bitmap index t1_color_indx on t1(color) tablespace indx;
analyze index t1_color_indx compute statistics;
analyze index t1_color_indx valudate structure;
select a.table_name, a.index_name, a.index_type, a.leef_blocks, b.height from user_indexes a.index_stats b where a.index_mane=b.index_name and a.index_name=’T1_COLOR_IND’;
set autostrade trace
select count(*) from t1 where color=‘red’;
set auto trace off
select * from t1 where id < 10;
update t1 set color = ‘blue’ where id = 1;
update t1 set color = ‘green’ where id = 2;(打开另一个会话)
rollback;
rollback;
set autotrace trace
select count(*) from t1 where color=‘red’ or color = ‘blue’;
su - oracle
|sql
e.g. : select rowid, ename, sal from emp；
rowid : 6 ：object_id, 3 ：file#， 6 ：block, 3 : row#
复合压缩索引 ：
全局hash索引 ：
反向索引 ：解决热块问题，不适合范围查询
平衡树索引（普通索引）：适合字段基数大，重复值少，DML代价比较低，适合OLTP环境
经常用于select语句中，where语句中，排序的字段适合建立索引
表级共享锁 share lock
行级排他锁 exclusive lock
段级位图锁
eg :
show parameter cpu
show parameter resoure
eg 资源管理器的创建 ：
官方文档 ：administrator
SQL 语句执行的三个过程 ：
parse解析 : 建立执行计划
execute执行 :
fetch取值从buffer cache里获取数据 :
硬解析 ：三步
软解析 ：
1. 在lib cache读取执行计划
2. execute plan
3. 从buffer cache读取数据块
LRU : 最近最少使用
eg :
alter system set result_cache_max_size=0;
show parameter result
alter system set result_cache_max_size=1536;(从0改为非0后，必须重启才能生效)
eg :
conn scott/tiger
select /*+ result_cache */ count(*) from emp;
set autotrace trace
r
r
1
show parameter result
alter system set result_cache_mode = force;
select /*+ result_cache */ count(*) from emp;
r
exec dbms_result_cache.flush;
r
r
select dbms_result_cache.status from dual;
shutdown immediate;
startup
select dbms_result_cache.status from dual;
show parameter result
alter system set result_cache_mode=manual;
conn scott/tiger
set autotrace trace
select count(*) from emp where empno=20;
select /*+ result_cache */ count(*) from emp where deptno=20;
exec dbms_result_cache.memory_report;
set serverout on
exec dbms_result_cache.memory_report;
eg :
select * from emp where deptno=:n;
结果缓存（官方文档 Performance Tuning Guide 7.6 Managing the server and client query cache)
统计分析 （官方文档 PL/SQL Package and Type Reference 或
SPA (SQL Performance Analyzer)
SQL性能优化分析
SPM(SQL Plan Management)
SQL执行计划管理
store outline 存储纲要
sql profile
hints 提示
稳定执行计划，根据访问对象的变化，实时调整新的计划
spm : sql执行计划管理
sql plan baseline : 执行计划基线(执行计划的集合)
eg :
show parameter optimizer
eg :
select * from tab;
create table emp1 select * from emp;
select * from emp1;
set autotrace on
select * from emp1 where empno=7788;
r
select sql_text, sql_id from v$sql where sql_text like ‘select * from emp%’; (查询sql id)
set serveroutput on
declare
`1_plans_loaded pls_integer；
begin
1_p;ans_loaded := DBMS_SPM.load_plans_from_cursor_cache(sql_id =>…);
DBMS_OUTPUT.put_line(‘Plans Loaded : || 1_plan_loaded);
end;
/
select sql_handle, plan_name, enabled, accepted from dba_sql_plan_baselines where sql_text like ‘%emp1%’ and sql_id not like ‘%dba%’ ;
create index
set autotrace on
select * from emp1 where empno = 7788;