引言：首先说明并行技术属于大数据范畴，适合OLAP系统，在任务分割、数据块分割、资源充裕的场合应用较广，本次分享主要概括并行原理、实际应用、性能对比、并行直接加载、索引属性、特点小结等六个小点去重点阐述。下面的测试是我的笔记，这些笔记也参考了《让oracle跑的更快2》作者：谭怀远 一书的引导，在此向谭总表示感谢，向帮助过我们的人表示感谢 zhixiang yangqiaojie等好友
一、简单介绍OLTP和OLAP系统的特点小结
答：OLTP和OLAP是我们大家在日常生产库中最常用到的2种系统，简单的说OLTP是基于多事务短时间片的系统，内存的效率决定了数据库的效率。
OLAP是基于大数据集长时间片的系统，SQL执行效率决定了数据库的效率。因此说“并行parallel”技术属于OLAP系统范畴
二、并行技术实现机制和场合
答：并行是相对于串行而言的，一个大的数据块分割成n个小的数据块，同时启动n个进程分别处理n个数据块，最后由并行协调器coordinater整合结果返回给用户。实际上在一个并行执行的过程中还存在着并行进程之间的通信问题（并行间的交互操作）。上面也说过并行是属于大数据处理的技术适合OLAP，并不适合OLTP，因为OLTP系统中的sql执行效率通常都是非常高的。
三、测试并行技术在实际中的应用和规则
（1)在有索引的表leo_t上使用并行技术，但没有起作用的情况
创建一张表
LS@LEO> create table leo_t as select rownum id ,object_name,object_type from dba_objects;
在表id列上创建索引
LS@LEO> create index leo_t_idx on leo_t(id);
收集表leo_t统计信息
LS@LEO> execute dbms_stats.gather_table_stats(ownname=>'LS',tabname=>'LEO_T',method_opt=>'for all indexed columns size 2',cascade=>TRUE);
为表启动4个并行度
LS@LEO> alter table leo_t parallel 4;
启动执行计划
LS@LEO> set autotrace trace explain stat
LS@LEO> select * from leo_t where id=100; 使用索引检索的数据，并没有启动并行
Execution Plan 执行计划
----------------------------------------------------------
Plan hash value: 2049660393
-----------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
-----------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 28 | 2 (0)| 00:00:01 |
| 1 | TABLE ACCESS BY INDEX ROWID| LEO_T | 1 | 28 | 2 (0)| 00:00:01 |
|* 2 | INDEX RANGE SCAN | LEO_T_IDX | 1 | | 1 (0)| 00:00:01 |
-----------------------------------------------------------------------------------------
Predicate Information (identified by operation id):
---------------------------------------------------
2 - access("ID"=100)
Statistics 统计信息
----------------------------------------------------------
1 recursive calls
0 db block gets
4 consistent gets 4次一致性读，即处理4个数据块
0 physical reads
0 redo size
544 bytes sent via SQL*Net to client
381 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed
说明：我们在这个表上启动了并行但没有起作用是因为CBO优化器使用了B-tree索引来检索的数据直接就定位到rowid（B-tree索引特点适合重复率比较低的字段），所以才发生了4个一致性读，发现使用索引效率非常高，资源代价比较小没有使用并行的必要了。
（2)读懂一个并行执行计划
LS@LEO> select object_type,count(*) from leo_t group by object_type; 对象类型分组统计
35 rows selected.
Execution Plan 并行执行计划
----------------------------------------------------------
Plan hash value: 852105030
------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 10337 | 111K| 6 (17)| 00:00:01 | | | |
| 1 | PX COORDINATOR | | | | | | | | |
| 2 | PX SEND QC (RANDOM) | :TQ10001 | 10337 | 111K| 6 (17)| 00:00:01 | Q1,01 | P->S | QC (RAND) |
| 3 | HASH GROUP BY | | 10337 | 111K| 6 (17)| 00:00:01 | Q1,01 | PCWP | |
| 4 | PX RECEIVE | | 10337 | 111K| 6 (17)| 00:00:01 | Q1,01 | PCWP | |
| 5 | PX SEND HASH | :TQ10000 | 10337 | 111K| 6 (17)| 00:00:01 | Q1,00 | P->P | HASH |
| 6 | HASH GROUP BY | | 10337 | 111K| 6 (17)| 00:00:01 | Q1,00 | PCWP | |
| 7 | PX BLOCK ITERATOR | | 10337 | 111K| 5 (0)| 00:00:01 | Q1,00 | PCWC | |
| 8 | TABLE ACCESS FULL| LEO_T | 10337 | 111K| 5 (0)| 00:00:01 | Q1,00 | PCWP | |
------------------------------------------------------------------------------------------------------------------
Statistics 统计信息
----------------------------------------------------------
44 recursive calls
0 db block gets
259 consistent gets 259次一致性读，即处理259个数据块
0 physical reads
0 redo size
1298 bytes sent via SQL*Net to client
403 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
1 sorts (memory)
0 sorts (disk)
35 rows processed
ps -ef | grep oracle 从后台进程上看也能发现起了4个并行进程和1个协调进程
oracle 25075 1 0 22:58 ? 00:00:00 ora_p000_LEO
oracle 25077 1 0 22:58 ? 00:00:00 ora_p001_LEO
oracle 25079 1 0 22:58 ? 00:00:00 ora_p002_LEO
oracle 25081 1 0 22:58 ? 00:00:00 ora_p003_LEO
oracle 25083 1 0 22:58 ? 00:00:00 ora_p004_LEO
说明：在进行分组整理的select中，会处理大量的数据集（发生了259次一致性读），这时使用并行来分割数据块处理可以提高效率，因此oracle使用了并行技术，解释一下并行执行计划步骤，并行执行计划应该从下往上读，当看见PX（parallel execution）关键字说明使用了并行技术
1.首先全表扫描
2.并行进程以迭代iterator的方式访问数据块，并将扫描结果提交给父进程做hash group
3.并行父进程对子进程传递过来的数据做hash group操作
4.并行子进程（PX SEND HASH）将处理完的数据发送出去，子和父是相对而言的，我们定义发送端为子进程，接收端为父进程
5.并行父进程（PX RECEIVE）将处理完的数据接收
6.按照随机顺序发送给并行协调进程QC（query coordinator）整合结果（对象类型分组统计）
7.完毕后QC将整合结果返回给用户
说明并行执行计划中特有的IN-OUT列的含义（指明了操作中数据流的方向）
Parallel to Serial（P->S）: 表示一个并行操作向一个串行操作发送数据，通常是将并行结果发送给并行调度进程QC进行汇总
Parallel to Parallel（P->P）：表示一个并行操作向另一个并行操作发送数据，一般是并行父进程与并行子进程之间的数据交流。
Parallel Combined with parent(PCWP): 同一个从属进程执行的并行操作，同时父操作也是并行的。
Parallel Combined with Child(PCWC): 同一个从属进程执行的并行操作，同时子操作也是并行的。
Serial to Parallel（S->P）: 表示一个串行操作向一个并行操作发送数据，如果select部分是串行操作，就会出现这个情况
（3）介绍4个我们常用的并行初始化参数
parallel_min_percent 50% 表示指定SQL并行度最小阀值才能执行，如果没有达到这个阀值，oracle将会报ora-12827错误
parallel_adaptive_multi_user TRUE 表示按照系统资源情况动态调整SQL并行度，已取得最好的执行性能
parallel_instance_group 表示在几个实例间起并行
parallel_max_servers 100 表示整个数据库实例的并行进程数不能超过这个值
parallel_min_servers 0 表示数据库启动时初始分配的并行进程数，如果我们设置的并行度小于这个值，并行协调进程会按我们的并行度来分配并行进程数，如果我们设置的并行度大于这个值，并行协调进程会额外启动其他的并行进程来满足我们的需求
（4）使用hint方式测试DML并行查询性能
首先说一下什么时候可以使用并行技术
1.对象属性：在创建的时候，就指定了并行关键字，长期有效
2.sql强制执行：在sql中使用hint提示方法使用并行，临时有效，它是约束sql语句的执行方式，本次测试就是使用的hint方式
LS@LEO> select /*+ parallel(leo_t 4) */ count(*) from leo_t where object_name in (select /*+ parallel(leo_t1 4) */ object_name from leo_t1);
Execution Plan 执行计划
----------------------------------------------------------
Plan hash value: 3814758652
-------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
-------------------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 94 | 16 (0)| 00:00:01 | | | |
| 1 | SORT AGGREGATE | | 1 | 94 | | | | | |
| 2 | PX COORDINATOR | | | | | | | | |
| 3 | PX SEND QC (RANDOM) | :TQ10002 | 1 | 94 | | | Q1,02 | P->S | QC (RAND) |
| 4 | SORT AGGREGATE | | 1 | 94 | | | Q1,02 | PCWP | |
|* 5 | HASH JOIN SEMI | | 10337 | 948K| 16 (0)| 00:00:01 | Q1,02 | PCWP | |
| 6 | PX RECEIVE | | 10337 | 282K| 5 (0)| 00:00:01 | Q1,02 | PCWP | |
| 7 | PX SEND HASH | :TQ10000 | 10337 | 282K| 5 (0)| 00:00:01 | Q1,00 | P->P | HASH |
| 8 | PX BLOCK ITERATOR | | 10337 | 282K| 5 (0)| 00:00:01 | Q1,00 | PCWC | |
| 9 | TABLE ACCESS FULL| LEO_T | 10337 | 282K| 5 (0)| 00:00:01 | Q1,00 | PCWP | |
| 10 | PX RECEIVE | | 10700 | 689K| 11 (0)| 00:00:01 | Q1,02 | PCWP | |
| 11 | PX SEND HASH | :TQ10001 | 10700 | 689K| 11 (0)| 00:00:01 | Q1,01 | P->P | HASH |
| 12 | PX BLOCK ITERATOR | | 10700 | 689K| 11 (0)| 00:00:01 | Q1,01 | PCWC | |
| 13 | TABLE ACCESS FULL| LEO_T1 | 10700 | 689K| 11 (0)| 00:00:01 | Q1,01 | PCWP | |
-------------------------------------------------------------------------------------------------------------------
并行先扫描子查询leo_t1表，然后对主查询leo_t表进行扫描，按照随机顺序发送到并行协调进程QC整合结果，最后将结果返回给用户
Predicate Information (identified by operation id):
---------------------------------------------------
5 - access("OBJECT_NAME"="OBJECT_NAME")
Note
-----
- dynamic sampling used for this statement
Statistics 统计信息
----------------------------------------------------------
28 recursive calls
0 db block gets
466 consistent gets 466次一致性读，即处理了446个数据块
0 physical reads
0 redo size
413 bytes sent via SQL*Net to client
381 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
2 sorts (memory)
0 sorts (disk)
1 rows processed
（5）并行DDL测试
使用10046事件生成文法追踪文件，level 12：包括sql语句解析、执行、提取、提交和回滚与等待事件，这是最高级别，而且向下兼容
10046事件解释：10046 event是oracle用于系统性能分析的重要事件。当激活这个事件后，将通知oracle kernel追踪会话的相关即时信息，并写入到相应trace文件中。这些有用的信息主要包括sql是如何进行解析，绑定变量的使用情况，会话中发生的等待事件等10046event 可分成不同的级别（level），分别追踪记录不同程度的有用信息。对于这些不同的级别，应当注意的是向下兼容的，即高一级的trace信息包含低于此级的所有信息。
启动10046事件命令：alter session set events '10046 trace name context forever,level 12';
关闭10046事件命令：alter session set events '10046 trace name context off';
注：oracle提供了一个tkprof工具来对trace文件进行格式化翻译，过滤出有用的信息
LS@LEO> alter session set events '10046 trace name context forever,level 12';
Session altered.
表对象属性，在创建的时候就直接指定好了并行度，后面我们会从trace文件中看出，已经列出了sql解析、执行、取操作的性能指标，后面又列出了等待事件，在等待事件中我们可以看到PX并行等待事件，说明使用了并行技术执行
S@LEO> create table leo_t2 parallel 4 as select * from dba_objects;
Table created.
格式化trace文件
$ pwd
/u01/app/oracle/admin/LEO/udump
$ tkprof leo_ora_20558.trc leo.txt sys=no
TKPROF: Release 10.2.0.1.0 - Production on Sat Aug 4 14:54:21 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
输出内容
create table leo_t2 parallel 4 as select * from dba_objects
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.01 0.03 0 0 1 0
Execute 1 0.41 4.26 199 2985 1176 10336
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 0.42 4.29 199 2985 1177 10336
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 27
Elapsed times include waiting on following events:
Event waited on 等待时间列表 Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
os thread startup 7 0.21 0.43
PX Deq: Join ACK 连接应答 5 0.01 0.05
PX qref latch 闩 2 0.01 0.01
PX Deq: Parse Reply 解析回复 4 0.17 0.23
enq: PS - contention 1 0.00 0.00
PX Deq: Execute Reply 执行回复 12 1.01 2.24
rdbms ipc reply 3 0.13 0.33
db file scattered read 3 0.00 0.00
log file sync 日志文件同步 2 0.00 0.00
PX Deq: Signal ACK 信号应答 4 0.01 0.01
SQL*Net message to client 1 0.00 0.00
SQL*Net message from client 1 0.00 0.00
********************************************************************************
索引对象属性，在创建索引的时候使用并行可以大大提高执行的效率，前提是系统资源充裕，否则可能适得其反哦：）
机制：把全部索引分成4份给4个并行进程去处理，把处理完的数据随机顺序发给QC整合结果，最后QC把最终结果返回给用户，完成sql操作
创建B-tree索引
LS@LEO> create index leo2_t_index on leo_t2(object_id) parallel 4;
Index created.
重建索引
LS@LEO> alter index leo2_t_index rebuild parallel 4;
Index altered.
输出内容
create index leo2_t_index on leo_t2(object_id) parallel 4
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 2 0.02 0.06 0 3 0 0
Execute 2 0.11 4.72 80 632 471 0
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 4 0.14 4.79 80 635 471 0
Misses in library cache during parse: 2
Optimizer mode: ALL_ROWS
Parsing user id: 27
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
os thread startup 10 0.04 0.25
PX Deq: Join ACK 10 0.01 0.02
enq: PS - contention 4 0.00 0.00
PX qref latch 37 0.09 0.37
PX Deq: Parse Reply 7 0.01 0.06
PX Deq: Execute Reply 81 1.96 3.15
PX Deq: Table Q qref 3 0.24 0.24
log file sync 2 0.00 0.00
PX Deq: Signal ACK 6 0.00 0.01
latch: session allocation 1 0.01 0.01
SQL*Net message to client 2 0.00 0.00
SQL*Net message from client 2 0.00 0.00
********************************************************************************
alter index leo2_t_index rebuild parallel 4
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 2 0.02 0.09 0 54 6 0
Execute 2 0.03 0.83 122 390 458 0
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 4 0.05 0.93 122 444 464 0
Misses in library cache during parse: 2
Optimizer mode: ALL_ROWS
Parsing user id: 27
Elapsed times include waiting on following events:
Event waited on Times Max. Wait Total Waited
---------------------------------------- Waited ---------- ------------
enq: PS - contention 3 0.00 0.00
PX Deq: Parse Reply 3 0.00 0.00
PX Deq: Execute Reply 84 0.06 0.40
PX qref latch 3 0.08 0.09
PX Deq: Table Q qref 4 0.00 0.01
log file sync 5 0.00 0.00
PX Deq: Signal ACK 7 0.00 0.00
reliable message 2 0.00 0.00
enq: RO - fast object reuse 2 0.00 0.00
db file sequential read 2 0.00 0.00
rdbms ipc reply 4 0.00 0.00
SQL*Net message to client 2 0.00 0.00
SQL*Net message from client 2 0.00 0.00
********************************************************************************
（6）并行DML测试
前提：首先说明oracle对并行操作是有限制的，必须设置启用会话并行度，否则即使SQL指定了并行，oracle也不会执行DML并行操作
其次oracle只对partition table分区表做并行处理（有几个分区就开几个并行），普通表oracle不做并行处理，只限delete update merge操作
LS@LEO> alter session enable parallel dml; 启动会话并行度
Session altered.
我的表leo_t1是普通表，liusheng_hash分区表（包括10个分区）
LS@LEO> explain plan for delete /*+ parallel(leo_t1 2) */ from leo_t1;
Explained.
LS@LEO> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT 执行计划，对于普通表即使设置了并行度，oracle也不做并行处理，看还是使用的全表扫描
--------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 3964128955
---------------------------------------------------------------------
| Id | Operation | Name | Rows | Cost (%CPU)| Time |
---------------------------------------------------------------------
| 0 | DELETE STATEMENT | | 10700 | 40 (0)| 00:00:01 |
| 1 | DELETE | LEO_T1 | | | |
| 2 | TABLE ACCESS FULL| LEO_T1 | 10700 | 40 (0)| 00:00:01 |
---------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement
LS@LEO> explain plan for delete /*+ parallel(liusheng_hash 2) */ from liusheng_hash;
Explained.
LS@LEO> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT 执行计划，oracle对于分区表是做并行处理的，从in-out字段上也可以看出并行全表扫描
--------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 1526574995
----------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Cost (%CPU)| Time | Pstart| Pstop | TQ |IN-OUT| PQ Distrib |
----------------------------------------------------------------------------------------------------------------------------
| 0 | DELETE STATEMENT | | 10996 | 26 (0)| 00:00:01 | | | | | |
| 1 | PX COORDINATOR | | | | | | | | | |
| 2 | PX SEND QC (RANDOM) | :TQ10000 | 10996 | 26 (0)| 00:00:01 | | | Q1,00 | P->S | QC (RAND) |
| 3 | DELETE | LIUSHENG_HASH | | | | | | Q1,00 | PCWP | |
| 4 | PX BLOCK ITERATOR | | 10996 | 26 (0)| 00:00:01 | 1 | 10 | Q1,00 | PCWC | |
| 5 | TABLE ACCESS FULL| LIUSHENG_HASH | 10996 | 26 (0)| 00:00:01 | 1 | 10 | Q1,00 | PCWP | |
----------------------------------------------------------------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement
LS@LEO> explain plan for update /*+ parallel(liusheng_hash 4) */ liusheng_hash set object_name=object_name||' ';
Explained.
LS@LEO> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT 执行计划 更新操作也是一样
--------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 225854777
------------------------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | Pstart| Pstop | TQ |IN-OUT| PQ Distrib |
------------------------------------------------------------------------------------------------------------------------------------
| 0 | UPDATE STATEMENT | | 10996 | 708K| 13 (0)| 00:00:01 | | | | | |
| 1 | PX COORDINATOR | | | | | | | | | | |
| 2 | PX SEND QC (RANDOM) | :TQ10000 | 10996 | 708K| 13 (0)| 00:00:01 | | | Q1,00 | P->S | QC (RAND) |
| 3 | UPDATE | LIUSHENG_HASH | | | | | | | Q1,00 | PCWP | |
| 4 | PX BLOCK ITERATOR | | 10996 | 708K| 13 (0)| 00:00:01 | 1 | 10 | Q1,00 | PCWC | |
| 5 | TABLE ACCESS FULL| LIUSHENG_HASH | 10996 | 708K| 13 (0)| 00:00:01 | 1 | 10 | Q1,00 | PCWP | |
------------------------------------------------------------------------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement
接下来做insert并行测试，在insert测试中只有insert into ...... select ......做并行才有意义，insert into ......values ......单条插入没有意义
LS@LEO> explain plan for insert /*+ parallel(leo_t1 4) */ into leo_t1 select /*+ parallel(leo_t2 4) */ * from leo_t2;
Explained.
LS@LEO> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT 执行计划 insert和select操作别分使用了并行，它们是相互独立的互不干涉
--------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 1922268564
-----------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
-----------------------------------------------------------------------------------------------------------------
| 0 | INSERT STATEMENT | | 10409 | 1799K| 11 (0)| 00:00:01 | | | |
| 1 | PX COORDINATOR | | | | | | | | |
| 2 | PX SEND QC (RANDOM) | :TQ10001 | 10409 | 1799K| 11 (0)| 00:00:01 | Q1,01 | P->S | QC (RAND) |
| 3 | LOAD AS SELECT | LEO_T1 | | | | | Q1,01 | PCWP | |
| 4 | PX RECEIVE | | 10409 | 1799K| 11 (0)| 00:00:01 | Q1,01 | PCWP | |
| 5 | PX SEND ROUND-ROBIN| :TQ10000 | 10409 | 1799K| 11 (0)| 00:00:01 | Q1,00 | P->P | RND-ROBIN |
| 6 | PX BLOCK ITERATOR | | 10409 | 1799K| 11 (0)| 00:00:01 | Q1,00 | PCWC | |
| 7 | TABLE ACCESS FULL| LEO_T2 | 10409 | 1799K| 11 (0)| 00:00:01 | Q1,00 | PCWP | |
-----------------------------------------------------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement
下面的insert语句没有在select使用并行，那么我们看看select语句是否用的串行操作
LS@LEO> explain plan for insert /*+ parallel(leo_t1 4) */ into leo_t1 select * from leo_t2;
Explained.
LS@LEO> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT 执行计划的in-out(进程间数据流)中可以看出S->P：Serial to Parallel一个串行操作（全表扫描）向一个并行操作发送数据，例如select子句是串行操作，所以就会出现这种情况
--------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 2695467291
------------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
------------------------------------------------------------------------------------------------------------------
| 0 | INSERT STATEMENT | | 10409 | 1799K| 40 (0)| 00:00:01 | | | |
| 1 | PX COORDINATOR | | | | | | | | |
| 2 | PX SEND QC (RANDOM) | :TQ10001 | 10409 | 1799K| 40 (0)| 00:00:01 | Q1,01 | P->S | QC (RAND) |
| 3 | LOAD AS SELECT | LEO_T1 | | | | | Q1,01 | PCWP | |
| 4 | BUFFER SORT | | | | | | Q1,01 | PCWC | |
| 5 | PX RECEIVE | | 10409 | 1799K| 40 (0)| 00:00:01 | Q1,01 | PCWP | |
| 6 | PX SEND ROUND-ROBIN| :TQ10000 | 10409 | 1799K| 40 (0)| 00:00:01 | | S->P | RND-ROBIN |
| 7 | TABLE ACCESS FULL | LEO_T2 | 10409 | 1799K| 40 (0)| 00:00:01 | | | |
------------------------------------------------------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement
下面的insert语句没有在insert使用并行，让我们看看效果怎么样
LS@LEO> explain plan for insert into leo_t1 select /*+ parallel(leo_t2 4) */ * from leo_t2;
Explained.
LS@LEO> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT 执行计划 TABLE ACCESS FULL - PCWP 全表扫描用的是并行，PX SEND QC (RANDOM) - P->S 表示一个并行操作向一个串行操作发送数据，这就表示了我们先用并行select后面insert用的是串行了
--------------------------------------------------------------------------------------------------------------------------------------
Plan hash value: 985193522
--------------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
--------------------------------------------------------------------------------------------------------------
| 0 | INSERT STATEMENT | | 10409 | 1799K| 11 (0)| 00:00:01 | | | |
| 1 | PX COORDINATOR | | | | | | | | |
| 2 | PX SEND QC (RANDOM)| :TQ10000 | 10409 | 1799K| 11 (0)| 00:00:01 | Q1,00 | P->S | QC (RAND) |
| 3 | PX BLOCK ITERATOR | | 10409 | 1799K| 11 (0)| 00:00:01 | Q1,00 | PCWC | |
| 4 | TABLE ACCESS FULL| LEO_T2 | 10409 | 1799K| 11 (0)| 00:00:01 | Q1,00 | PCWP | |
--------------------------------------------------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement
（7）使用并行的3种方法
1.hint 方式 临时有效
LS@LEO> set autotrace trace exp
LS@LEO> select /*+ parallel(leo_t1 4) */ * from leo_t1;
LS@LEO> select /*+ parallel(leo_t1 4) */ count(*) from leo_t1;
Execution Plan 执行计划 hint方式
----------------------------------------------------------
Plan hash value: 2648044456
--------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
--------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 11 (0)| 00:00:01 | | | |
| 1 | SORT AGGREGATE | | 1 | | | | | |
| 2 | PX COORDINATOR | | | | | | | |
| 3 | PX SEND QC (RANDOM) | :TQ10000 | 1 | | | Q1,00 | P->S | QC (RAND) |
| 4 | SORT AGGREGATE | | 1 | | | Q1,00 | PCWP | |
| 5 | PX BLOCK ITERATOR | | 10700 | 11 (0)| 00:00:01 | Q1,00 | PCWC | |
| 6 | TABLE ACCESS FULL| LEO_T1 | 10700 | 11 (0)| 00:00:01 | Q1,00 | PCWP | |
--------------------------------------------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement
2.alter table 定义方式 长期有效
LS@LEO> alter table leo_t1 parallel 4;
Table altered.
LS@LEO> select count(*) from leo_t1;
Execution Plan 执行计划 定义方式
----------------------------------------------------------
Plan hash value: 2648044456
--------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
--------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 11 (0)| 00:00:01 | | | |
| 1 | SORT AGGREGATE | | 1 | | | | | |
| 2 | PX COORDINATOR | | | | | | | |
| 3 | PX SEND QC (RANDOM) | :TQ10000 | 1 | | | Q1,00 | P->S | QC (RAND) |
| 4 | SORT AGGREGATE | | 1 | | | Q1,00 | PCWP | |
| 5 | PX BLOCK ITERATOR | | 10700 | 11 (0)| 00:00:01 | Q1,00 | PCWC | |
| 6 | TABLE ACCESS FULL| LEO_T1 | 10700 | 11 (0)| 00:00:01 | Q1,00 | PCWP | |
--------------------------------------------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement
3.alter session force parallel 强制定义并行度
LS@LEO> alter table leo_t1 parallel 1; 首先我们已经修改并行度为1
Table altered.
LS@LEO> alter session force parallel query parallel 4; 再次强制定义并行度为4
Session altered.
LS@LEO> select count(*) from leo_t1;
Execution Plan 执行计划 强制使用并行度4执行SQL
----------------------------------------------------------
Plan hash value: 2648044456
--------------------------------------------------------------------------------------------------------
| Id | Operation | Name | Rows | Cost (%CPU)| Time | TQ |IN-OUT| PQ Distrib |
--------------------------------------------------------------------------------------------------------
| 0 | SELECT STATEMENT | | 1 | 11 (0)| 00:00:01 | | | |
| 1 | SORT AGGREGATE | | 1 | | | | | |
| 2 | PX COORDINATOR | | | | | | | |
| 3 | PX SEND QC (RANDOM) | :TQ10000 | 1 | | | Q1,00 | P->S | QC (RAND) |
| 4 | SORT AGGREGATE | | 1 | | | Q1,00 | PCWP | |
| 5 | PX BLOCK ITERATOR | | 10700 | 11 (0)| 00:00:01 | Q1,00 | PCWC | |
| 6 | TABLE ACCESS FULL| LEO_T1 | 10700 | 11 (0)| 00:00:01 | Q1,00 | PCWP | |
--------------------------------------------------------------------------------------------------------
Note
-----
- dynamic sampling used for this statement
（8）/*+ append */直接加载
直接加载：指数据不经过db_buffer_cache内存区，直接写入到数据文件中，实际上是直接追加到数据段的最后，不在段中寻找空闲空间而插入
LS@LEO> create table leo_t3 as select * from dba_objects; 创建表leo_t3
Table created.
LS@LEO> insert /*+ append*/ into leo_t3 select * from dba_objects; 直接加载数据
10337 rows created.
LS@LEO> create table leo_t4 as select * from leo_t3 where rownum<10000; 创建表leo_t4
Table created.
LS@LEO> select segment_name,extent_id,bytes from user_extents where segment_name='LEO_T4'; 表leo_t4占用了16个区
SEGMENT_NAME EXTENT_ID BYTES
--------------------------------------------------------------------------------- ---------- ----------
LEO_T4 0 65536
LEO_T4 1 65536
LEO_T4 2 65536
LEO_T4 3 65536
LEO_T4 4 65536
LEO_T4 5 65536
LEO_T4 6 65536
LEO_T4 7 65536
LEO_T4 8 65536
LEO_T4 9 65536
LEO_T4 10 65536
LEO_T4 11 65536
LEO_T4 12 65536
LEO_T4 13 65536
LEO_T4 14 65536
LEO_T4 15 65536
LEO_T4 16 1048576
LS@LEO> delete from leo_t4; 删除所有记录
9999 rows deleted.
LS@LEO> commit; 提交
Commit complete.
LS@LEO> select segment_name,extent_id,bytes from user_extents where segment_name='LEO_T4'; 删除之后为什么还占用16个区呢，我来解释一下，oracle在delete操作后数据并没有真实的删除了。只是打上一个“标记”说明这些数据不可用了，也说明了为什么删除之后磁盘空间没有回收的问题。
SEGMENT_NAME EXTENT_ID BYTES
--------------------------------------------------------------------------------- ---------- ----------
LEO_T4 0 65536
LEO_T4 1 65536
LEO_T4 2 65536
LEO_T4 3 65536
LEO_T4 4 65536
LEO_T4 5 65536
LEO_T4 6 65536
LEO_T4 7 65536
LEO_T4 8 65536
LEO_T4 9 65536
LEO_T4 10 65536
LEO_T4 11 65536
LEO_T4 12 65536
LEO_T4 13 65536
LEO_T4 14 65536
LEO_T4 15 65536
LEO_T4 16 1048576
LS@LEO> insert into leo_t4 select * from leo_t3 where rownum<10000; 传统加载 oracle会找段中的空闲空间插入数据，看还是利旧了原来的16个区
9999 rows created.
LS@LEO> select segment_name,extent_id,bytes from user_extents where segment_name='LEO_T4';
SEGMENT_NAME EXTENT_ID BYTES
--------------------------------------------------------------------------------- ---------- ----------
LEO_T4 0 65536
LEO_T4 1 65536
LEO_T4 2 65536
LEO_T4 3 65536
LEO_T4 4 65536
LEO_T4 5 65536
LEO_T4 6 65536
LEO_T4 7 65536
LEO_T4 8 65536
LEO_T4 9 65536
LEO_T4 10 65536
LEO_T4 11 65536
LEO_T4 12 65536
LEO_T4 13 65536
LEO_T4 14 65536
LEO_T4 15 65536
LEO_T4 16 1048576
LS@LEO> delete from leo_t4; 删除所有记录
9999 rows deleted.
LS@LEO> commit;
Commit complete.
LS@LEO> select count(*) from leo_t4; 记录数为0
COUNT(*)
----------
0
LS@LEO> select segment_name,extent_id,bytes from user_extents where segment_name='LEO_T4'; 这个表还是占用16个区，数据块有数据但是可以覆盖，我们认为是空闲的块
SEGMENT_NAME EXTENT_ID BYTES
--------------------------------------------------------------------------------- ---------- ----------
LEO_T4 0 65536
LEO_T4 1 65536
LEO_T4 2 65536
LEO_T4 3 65536
LEO_T4 4 65536
LEO_T4 5 65536
LEO_T4 6 65536
LEO_T4 7 65536
LEO_T4 8 65536
LEO_T4 9 65536
LEO_T4 10 65536
LEO_T4 11 65536
LEO_T4 12 65536
LEO_T4 13 65536
LEO_T4 14 65536
LEO_T4 15 65536
LEO_T4 16 1048576
LS@LEO> insert /*+ append */ into leo_t4 select * from leo_t3 where rownum<10000; 直接加载方式，oracle把新数据直接插入到新的20个区里了，并没有使用原来的16个区空闲块，也就应了不在段中寻找空闲块插入
9999 rows created.
LS@LEO> commit; 必须commit之后，oracle才讲HWM高水位线移动到新数据块之上，如果没有commit，oracle不会移动HWM高水位线，因此看不到数据字典里面的变化（也就是不显示后面的20个区），如果此时回滚的话，HWM高水位线不用动，就想什么都没有发生一样
Commit complete.
LS@LEO> select segment_name,extent_id,bytes from user_extents where segment_name='LEO_T4';
SEGMENT_NAME EXTENT_ID BYTES
--------------------------------------------------------------------------------- ---------- ----------
LEO_T4 0 65536
LEO_T4 1 65536
LEO_T4 2 65536
LEO_T4 3 65536
LEO_T4 4 65536
LEO_T4 5 65536
LEO_T4 6 65536
LEO_T4 7 65536
LEO_T4 8 65536
LEO_T4 9 65536
LEO_T4 10 65536
LEO_T4 11 65536
LEO_T4 12 65536
LEO_T4 13 65536
LEO_T4 14 65536
LEO_T4 15 65536
LEO_T4 16 65536
LEO_T4 17 65536
LEO_T4 18 65536
LEO_T4 19 65536
LEO_T4 20 65536
LEO_T4 21 65536
LEO_T4 22 65536
LEO_T4 23 65536
LEO_T4 24 65536
LEO_T4 25 65536
LEO_T4 26 65536
LEO_T4 27 65536
LEO_T4 28 65536
LEO_T4 29 65536
LEO_T4 30 65536
LEO_T4 31 65536
LEO_T4 32 65536
LEO_T4 33 65536
LEO_T4 34 65536
LEO_T4 35 65536
LEO_T4 36 65536
37 rows selected.
（9）/*+ append */直接加载和redo
LS@LEO> create table leo_t5 as select object_id,object_name from dba_objects; 创建表leo_t5
Table created.
LS@LEO> create table leo_t6 as select object_id,object_name from dba_objects; 创建表leo_t6
Table created.
LS@LEO> alter table leo_t5 logging; 设置产生redo日志模式
Table altered.
LS@LEO> truncate table leo_t5; 截断表
Table truncated.
LS@LEO> set autotrace trace stat; 启动统计信息
insert into leo_t5 select * from leo_t6; 传统加载
LS@LEO>
10340 rows created.
Statistics 统计信息
----------------------------------------------------------
197 recursive calls
185 db block gets
92 consistent gets
60 physical reads
37128 redo size 37128 redo量
664 bytes sent via SQL*Net to client
571 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
3 sorts (memory)
0 sorts (disk)
10340 rows processed
LS@LEO> rollback; 回滚
Rollback complete.
LS@LEO> insert /*+ append */ into leo_t5 select * from leo_t6; 直接加载
10340 rows created.
Statistics
----------------------------------------------------------
111 recursive calls
180 db block gets
79 consistent gets
21 physical reads
36640 redo size 36640 redo量
664 bytes sent via SQL*Net to client
585 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
2 sorts (memory)
0 sorts (disk)
10340 rows processed
小结：我们看到传统加载和直接加载产生的redo量并没有太大的差异，因为只要底层数据块发生变化，就会生成redo信息，不管传统和直接都会修改数据块，用来恢复依据，所以并没有太大的差异。
（10）直接加载和索引
LS@LEO> set autotrace trace stat;
LS@LEO> insert /*+ append */ into leo_t5 select * from leo_t6; 直接加载，但表上没有索引
10340 rows created.
Statistics 统计信息
----------------------------------------------------------
111 recursive calls
175 db block gets
81 consistent gets
15 physical reads
36816 redo size 36816 redo量
664 bytes sent via SQL*Net to client
585 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
2 sorts (memory)
0 sorts (disk)
10340 rows processed
LS@LEO> create index leo_t5_index on leo_t5(object_id); 给表创建索引
Index created.
LS@LEO> rollback; 回滚
Rollback complete.
LS@LEO> insert /*+ append */ into leo_t5 select * from leo_t6; 直接加载，但表上有索引
10340 rows created.
Statistics 统计信息
----------------------------------------------------------
120 recursive calls
193 db block gets
85 consistent gets
22 physical reads
37344 redo size 37344 redo量
664 bytes sent via SQL*Net to client
585 bytes received via SQL*Net from client
4 SQL*Net roundtrips to/from client
3 sorts (memory)
0 sorts (disk)
10340 rows processed
小结：因为有了索引，直接加载redo量比没有索引时有一定的提升，可能是我的测试数据少所以这种提升并不明显，如果在实际生产库上发生了大量的redo，建议先将索引drop，加载数据后，在重建rebuild索引
（11）直接加载和并行
直接加载和并行是可以一起使用的，以此大幅度提高sql执行效率
LS@LEO> alter session enable parallel dml; 设置会话并行度
Session altered.
LS@LEO> alter session set events '10046 trace name context forever,level 12'; 使用trace文件跟踪sql性能指标
Session altered.
LS@LEO> insert /*+ append parallel(leo_t5,2) */ into leo_t5 select * from leo_t6; 直接加载+并行插入
10340 rows created.
LS@LEO> rollback;
Rollback complete.
LS@LEO> insert /*+ parallel(leo_t5,2) */ into leo_t5 select * from leo_t6; 并行插入
10340 rows created.
LS@LEO> rollback;
Rollback complete.
LS@LEO> insert /*+ append */ into leo_t5 select * from leo_t6; 直接加载
10340 rows created.
LS@LEO> rollback;
Rollback complete.
LS@LEO> insert into leo_t5 select * from leo_t6; 什么特性也没有用
10340 rows created.
LS@LEO> commit; 提交
Commit complete.
$ tkprof leo_ora_20558.trc leo.txt sys=no 格式化trace文件
TKPROF: Release 10.2.0.1.0 - Production on Sun Aug 5 22:13:38 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
insert /*+ append parallel(leo_t5,2) */ into leo_t5 select * from leo_t6
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.01 0 1 0 0
Execute 1 0.03 2.51 8 46 67 10340
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 0.04 2.53 8 47 67 10340
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 27
Rows Row Source Operation
------- ---------------------------------------------------
2 PX COORDINATOR (cr=46 pr=0 pw=0 time=2201632 us)
0 PX SEND QC (RANDOM) :TQ10001 (cr=0 pr=0 pw=0 time=0 us)
0 LOAD AS SELECT (cr=0 pr=0 pw=0 time=0 us)
0 BUFFER SORT (cr=0 pr=0 pw=0 time=0 us)
0 PX RECEIVE (cr=0 pr=0 pw=0 time=0 us)
0 PX SEND ROUND-ROBIN :TQ10000 (cr=0 pr=0 pw=0 time=0 us)
10340 TABLE ACCESS FULL LEO_T6 (cr=42 pr=0 pw=0 time=1356361 us)
insert /*+ parallel(leo_t5,2) */ into leo_t5 select * from leo_t6
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.01 0 1 0 0
Execute 1 0.02 1.66 7 44 64 10340
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 0.02 1.67 7 45 64 10340
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 27
Rows Row Source Operation
------- ---------------------------------------------------
2 PX COORDINATOR (cr=44 pr=0 pw=0 time=1209712 us)
0 PX SEND QC (RANDOM) :TQ10001 (cr=0 pr=0 pw=0 time=0 us)
0 LOAD AS SELECT (cr=0 pr=0 pw=0 time=0 us)
0 BUFFER SORT (cr=0 pr=0 pw=0 time=0 us)
0 PX RECEIVE (cr=0 pr=0 pw=0 time=0 us)
0 PX SEND ROUND-ROBIN :TQ10000 (cr=0 pr=0 pw=0 time=0 us)
10340 TABLE ACCESS FULL LEO_T6 (cr=42 pr=0 pw=0 time=186185 us)
insert /*+ append */ into leo_t5 select * from leo_t6
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 1 0 0
Execute 1 0.06 0.24 62 113 373 10340
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 0.06 0.24 62 114 373 10340
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 27
Rows Row Source Operation
------- ---------------------------------------------------
1 LOAD AS SELECT (cr=113 pr=62 pw=39 time=241775 us)
10340 TABLE ACCESS FULL LEO_T6 (cr=42 pr=0 pw=0 time=62104 us) 没有使用并行操作
insert into leo_t5 select * from leo_t6
call count cpu elapsed disk query current rows
------- ------ -------- ---------- ---------- ---------- ---------- ----------
Parse 1 0.00 0.00 0 43 0 0
Execute 1 0.14 0.54 100 101 1022 10340
Fetch 0 0.00 0.00 0 0 0 0
------- ------ -------- ---------- ---------- ---------- ---------- ----------
total 2 0.15 0.55 100 144 1022 10340
Misses in library cache during parse: 1
Optimizer mode: ALL_ROWS
Parsing user id: 27
Rows Row Source Operation
------- ---------------------------------------------------
10340 TABLE ACCESS FULL LEO_T6 (cr=42 pr=0 pw=0 time=744520 us) 只有全表扫描
小结：insert /*+ append parallel(leo_t5,2) */ into leo_t5 select * from leo_t6和insert /*+ parallel(leo_t5,2) */ into leo_t5 select * from leo_t6执行计划是一样的，因为当使用parallel并行插入时，oracle默认使用直接加载方式来加载数据，因此append关键字可忽略了。
注：如果执行alter session disable parallel dml; oracle就会禁用DML并行操作，就算有hint提示也不会起作用，那么insert /*+ append parallel(leo_t5,2) */和insert /*+ append */的执行计划都应该是一样的了，都是只有直接加载，没有并行效果了
（12）直接加载和sqlload
sqlload 是我们常用的文本加载工具，它可以把文本文件按照一定的格式批量加载到数据库中去，现在我们测试传统加载conventional、直接加载direct、并行parallel直接加载的性能对比和执行效率。
-rwxrwxrwx 1 oracle oinstall 283 Aug 9 00:11 leo_test.ctl 控制文件
-rwxrwxrwx 1 oracle oinstall 8983596 Aug 8 20:57 leo_test.data 数据文件，10万行数据，9个字段
-rwxrwxrwx 1 oracle oinstall 2099 Aug 9 00:15 leo_test.log 日志文件
1.传统加载conventional 10万行记录->表LEO_TEST_SQLLOAD
sqlldr userid=ls/ls control=leo_test.ctl 传统加载数据
LS@LEO> select count(*) from leo_test_sqlload;
COUNT(*)
----------
100000
SQL*Loader: Release 10.2.0.1.0 - Production on Thu Aug 9 00:14:15 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Control File: leo_test.ctl 控制文件
Data File: /home/oracle/leo_test.data 数据文件
Bad File: leo_test.bad 坏文件
Discard File: none specified
(Allow all discards)
Number to load: ALL
Number to skip: 0
Errors allowed: 50
Bind array: 64 rows, maximum of 256000 bytes
Continuation: none specified
Path used: Conventional sqlload采用传统加载方式，数据要通过缓冲区加载到表中
Table LEO_TEST_SQLLOAD, loaded from every logical record.
Insert option in effect for this table: APPEND 采用追加的方式加载，新数据不覆盖旧数据，而是结尾累加
TRAILING NULLCOLS option in effect
Column Name Position Len Term Encl Datatype 列信息
------------------------------ ---------- ----- ---- ---- ---------------------
START_TIME FIRST * | DATE YYYY-MM-DD HH24:MI:SS
END_TIME NEXT * | DATE YYYY-MM-DD HH24:MI:SS
PROTOCOL NEXT * | CHARACTER
PRIVATE_IP NEXT * | CHARACTER
PRIVATE_PORT NEXT * | CHARACTER
SRC_IP NEXT * | CHARACTER
SRC_PORT NEXT * | CHARACTER
DEST_IP NEXT * | CHARACTER
DEST_PORT NEXT * | CHARACTER
Table LEO_TEST_SQLLOAD:
100000 Rows successfully loaded. 10万行记录成功加载
0 Rows not loaded due to data errors.
0 Rows not loaded because all WHEN clauses were failed.
0 Rows not loaded because all fields were null.
Space allocated for bind array: 148608 bytes(64 rows)
Read buffer bytes: 1048576
Total logical records skipped: 0
Total logical records read: 100000
Total logical records rejected: 0
Total logical records discarded: 0
Run began on Thu Aug 09 00:14:15 2012
Run ended on Thu Aug 09 00:15:21 2012
Elapsed time was: 00:01:05.60 耗时65秒
CPU time was: 00:00:00.81
2.直接加载direct 10万行记录->表LEO_TEST_SQLLOAD1
LS@LEO> select df.tablespace_name "表空间名",totalspace "总空间M",freespace "剩余空间M",round((1-freespace/totalspace)*100,2) "使用率%"
from (select tablespace_name,round(sum(bytes)/1024/1024) totalspace from dba_data_files group by tablespace_name) df,
(select tablespace_name,round(sum(bytes)/1024/1024) freespace from dba_free_space group by tablespace_name) fs
where df.tablespace_name=fs.tablespace_name order by df.tablespace_name ; 2 3 4 5
表空间名 总空间M 剩余空间M 使用率%
------------------------------ ---------- ------------- ----------
CTXSYS 32 27 15.63
EXAMPLE 200 199 .5
SYSAUX 325 266 18.15
SYSTEM 325 84 74.15
UNDOTBS 200 189 5.5
USERS 600 501 16.5 没有加载表leo_test_sqlload1之前空间情况
sqlldr userid=ls/ls control=leo_test1.ctl data=leo_test.data log=leo_test1.log direct=true 直接加载10万行数据
LS@LEO> select count(*) from leo_test_sqlload1;
COUNT(*)
----------
100000 （3M）
LS@LEO> select df.tablespace_name "表空间名",totalspace "总空间M",freespace "剩余空间M",round((1-freespace/totalspace)*100,2) "使用率%"
from
(select tablespace_name,round(sum(bytes)/1024/1024) totalspace from dba_data_files group by tablespace_name) df,
(select tablespace_name,round(sum(bytes)/1024/1024) freespace from dba_free_space group by tablespace_name) fs
where df.tablespace_name=fs.tablespace_name order by df.tablespace_name ; 2 3 4 5
表空间名 总空间M 剩余空间M 使用率%
------------------------------ ---------- ------------- ----------
CTXSYS 32 27 15.63
EXAMPLE 200 199 .5
SYSAUX 325 266 18.15
SYSTEM 325 84 74.15
UNDOTBS 200 189 5.5
USERS 600 498 17 10万行记录加载后使用了3M空间
SQL*Loader: Release 10.2.0.1.0 - Production on Thu Aug 9 01:07:52 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Control File: leo_test1.ctl 控制文件
Data File: leo_test.data 数据文件，10万行数据，9个字段
Bad File: leo_test.bad 坏文件
Discard File: none specified
(Allow all discards)
Number to load: ALL
Number to skip: 0
Errors allowed: 50
Continuation: none specified
Path used: Direct sqlload采用直接加载方式，数据不通过缓冲区和sql语法引擎直接加载到表中
Table LEO_TEST_SQLLOAD1, loaded from every logical record.
Insert option in effect for this table: APPEND 采用追加的方式加载，新数据不覆盖旧数据，而是结尾累加
TRAILING NULLCOLS option in effect
Column Name Position Len Term Encl Datatype 列信息
------------------------------ ---------- ----- ---- ---- ---------------------
START_TIME FIRST * | DATE YYYY-MM-DD HH24:MI:SS
END_TIME NEXT * | DATE YYYY-MM-DD HH24:MI:SS
PROTOCOL NEXT * | CHARACTER
PRIVATE_IP NEXT * | CHARACTER
PRIVATE_PORT NEXT * | CHARACTER
SRC_IP NEXT * | CHARACTER
SRC_PORT NEXT * | CHARACTER
DEST_IP NEXT * | CHARACTER
DEST_PORT NEXT * | CHARACTER
Table LEO_TEST_SQLLOAD1:
100000 Rows successfully loaded. 10万行记录成功加载，占用3M磁盘空间
0 Rows not loaded due to data errors.
0 Rows not loaded because all WHEN clauses were failed.
0 Rows not loaded because all fields were null.
Date cache:
Max Size: 1000
Entries : 65
Hits : 199935
Misses : 0
Bind array size not used in direct path.
Column array rows : 5000
Stream buffer bytes: 256000
Read buffer bytes: 1048576
Total logical records skipped: 0
Total logical records read: 100000
Total logical records rejected: 0
Total logical records discarded: 0
Total stream buffers loaded by SQL*Loader main thread: 26
Total stream buffers loaded by SQL*Loader load thread: 17
Run began on Thu Aug 09 01:07:52 2012
Run ended on Thu Aug 09 01:07:56 2012
Elapsed time was: 00:00:03.53 耗时3秒.53 比 传统加载65秒节约了94%时间
CPU time was: 00:00:00.25
小结：因此我们知道直接加载要比传统加载执行效率高很多，当我们的系统负载不高，资源充裕时可以考虑使用直接加载direct方式批量导入数据，即减少了I/O和内存开销，又提高了数据加载效率。
3.并行直接加载direct 10万行记录->表LEO_TEST_SQLLOAD2
表空间名 总空间M 剩余空间M 使用率%
------------------------------ ---------- ------------- ----------
USERS 600 498 17 没有加载前表空间的空间状态
sqlldr userid=ls/ls control=leo_test2.ctl data=leo_test.data log=leo_test2.log direct=true parallel=true 并行直接加载10万行数据
LS@LEO> select count(*) from leo_test_sqlload2;
COUNT(*)
----------
100000 （8M）
表空间名 总空间M 剩余空间M 使用率%
------------------------------ ---------- ------------- ----------
USERS 600 490 18.33 10万行记录加载后使用了8M空间
SQL*Loader: Release 10.2.0.1.0 - Production on Thu Aug 9 07:25:00 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Control File: leo_test2.ctl 控制文件
Data File: leo_test.data 数据文件，10万行数据，9个字段
Bad File: leo_test.bad 坏文件
Discard File: none specified
(Allow all discards)
Number to load: ALL
Number to skip: 0
Errors allowed: 50
Continuation: none specified
Path used: Direct - with parallel option. sqlload采用并行+直接加载方式，既有并行，又有直接加载，双重功效，效率更高
Table LEO_TEST_SQLLOAD2, loaded from every logical record.
Insert option in effect for this table: APPEND 采用追加的方式加载，新数据不覆盖旧数据，而是结尾累加
TRAILING NULLCOLS option in effect
Column Name Position Len Term Encl Datatype 列信息
------------------------------ ---------- ----- ---- ---- ---------------------
START_TIME FIRST * | DATE YYYY-MM-DD HH24:MI:SS
END_TIME NEXT * | DATE YYYY-MM-DD HH24:MI:SS
PROTOCOL NEXT * | CHARACTER
PRIVATE_IP NEXT * | CHARACTER
PRIVATE_PORT NEXT * | CHARACTER
SRC_IP NEXT * | CHARACTER
SRC_PORT NEXT * | CHARACTER
DEST_IP NEXT * | CHARACTER
DEST_PORT NEXT * | CHARACTER
Table LEO_TEST_SQLLOAD2:
100000 Rows successfully loaded. 10万行记录成功加载，占用8M磁盘空间
0 Rows not loaded due to data errors.
0 Rows not loaded because all WHEN clauses were failed.
0 Rows not loaded because all fields were null.
Date cache:
Max Size: 1000
Entries : 65
Hits : 199935
Misses : 0
Bind array size not used in direct path.
Column array rows : 5000
Stream buffer bytes: 256000
Read buffer bytes: 1048576
Total logical records skipped: 0
Total logical records read: 100000
Total logical records rejected: 0
Total logical records discarded: 0
Total stream buffers loaded by SQL*Loader main thread: 26
Total stream buffers loaded by SQL*Loader load thread: 17
Run began on Thu Aug 09 07:25:00 2012
Run ended on Thu Aug 09 07:25:13 2012
Elapsed time was: 00:00:12.77 耗时00:00:12.77 比 直接加载3秒.53节约了93%时间
CPU time was: 00:00:00.98
小结：从时间成本上我们就可看出，并行直接加载效率要远远的高出串行直接加载，在海量数据的环境中使用并行和直接加载的技术，对提高效率和性能那是如虎添翼（并行并不一定比串行好，主要看业务类型其次看资源情况），我们应该思考“理解技术如何为业务服务”，这要比单纯学技术更加重要，谢谢！！！
（13）sqlload直接加载对索引的影响
所谓对索引的影响是指使用sqlload加载存在索引的表的数据时索引是否有效
非约束索引：sqlload直接加载完毕后维护索引的完整性，此时索引不失效
约束索引：例如 主键 外键 唯一索引 sqlload直接加载完毕后，数据会入库但索引会失效unusable，此时要重建索引
1.非约束索引，直接加载完毕后维护索引的完整性，此时索引不失效
LS@LEO> select count(*) from leo_test_sqlload1; 表中有10条记录
COUNT(*)
----------
100000
LS@LEO> create index leo_test_sqlload1_index on leo_test_sqlload1(private_ip); 在private_ip上创建B-tree索引
Index created.
LS@LEO> select status from user_indexes where table_name='LEO_TEST_SQLLOAD1'; 检查索引的有效性valid
STATUS
--------
VALID
sqlldr userid=ls/ls control=leo_test1.ctl data=leo_test.data log=leo_test1.log direct=true 直接加载后会维护索引的完整性
SQL*Loader: Release 10.2.0.1.0 - Production on Thu Aug 9 15:27:03 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Load completed - logical record count 100000. 10万行记录成功加载
LS@LEO> select count(*) from leo_test_sqlload1; 现在表中有20万条记录
COUNT(*)
----------
200000
LS@LEO> select status from user_indexes where table_name='LEO_TEST_SQLLOAD1'; 自动维护索引的有效性vaild，对非约束索引而言
STATUS
--------
VALID
2.约束索引：例如 主键 外键 唯一索引 sqlload直接加载完毕后，数据会入库但索引会失效unusable，此时要重建索引
LS@LEO> create table leo_test_sqlload3
(
START_TIME date,
END_TIME date,
PROTOCOL varchar(20),
PRIVATE_IP varchar(20),
PRIVATE_PORT varchar(20) constraint pk_leo_test_sqlload3 primary key , 我们创建一个带主键的表
SRC_IP varchar(20),
SRC_PORT varchar(20),
DEST_IP varchar(20),
DEST_PORT varchar(20)
);
Table created.
LS@LEO> select * from leo_test_sqlload3; 现在表中没有数据
no rows selected
sqlldr userid=ls/ls control=leo_test3.ctl data=leo_test1.data log=leo_test3.log direct=true
SQL*Loader: Release 10.2.0.1.0 - Production on Thu Aug 9 15:49:10 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Load completed - logical record count 100. 100行记录成功加载
LS@LEO> select * from leo_test_sqlload3; 数据已加载，但PRIVATE_PORT主键索引已经失效，因为我们的值全是一样的
START_TIME END_TIME PR PRIVATE_IP PRIV SRC_IP SRC_PORT DEST_IP DEST
---------------------- ---------------------- -- ------------ ---- ------------ -------- ------------ ----
2012-08-08 20:59:54 2012-08-08 21:00:28 6 2886756061 1111 3395517721 45031 3419418065 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886900807 1111 3395507143 51733 3658060738 80
2012-08-08 20:59:55 2012-08-08 21:00:28 6 2886917742 1111 3395507159 43516 2071873572 80
2012-08-08 20:59:55 2012-08-08 21:00:28 6 2886917742 1111 3395507159 43534 2071873572 80
2012-08-08 20:59:55 2012-08-08 21:00:28 6 2886917742 1111 3395507159 43523 2071873572 80
2012-08-08 21:00:14 2012-08-08 21:00:28 6 2886832065 1111 3395507109 51442 2099718013 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886794376 1111 3395507104 57741 2071819251 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886758392 1111 3395517723 56875 1007173560 80
2012-08-08 21:00:22 2012-08-08 21:00:28 6 2886862137 1111 3395517760 17744 3626142915 7275
2012-08-08 21:00:25 2012-08-08 21:00:28 6 2886741689 1111 3395517708 14954 2007469330 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886891044 1111 3395517787 23626 1872834975 443
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886790049 1111 3395507100 54215 1884995806 80
2012-08-08 21:00:15 2012-08-08 21:00:28 6 2886771544 1111 3395507083 32261 1872832004 80
2012-08-08 21:00:24 2012-08-08 21:00:28 6 2886796616 1111 3395517729 18634 2007467546 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886839912 1111 3395507117 10102 1850510469 5242
2012-08-08 21:00:23 2012-08-08 21:00:28 6 2886742978 1111 3395517709 28276 1021181676 80
2012-08-08 21:00:16 2012-08-08 21:00:28 6 2886792600 1111 3395507103 15204 974546887 80
2012-08-08 21:00:23 2012-08-08 21:00:28 6 2886890096 1111 3395517786 30741 1884983225 80
2012-08-08 21:00:00 2012-08-08 21:00:28 6 2886743885 1111 3395517710 18678 1884968358 80
2012-08-08 21:00:16 2012-08-08 21:00:28 6 2886792600 1111 3395507103 15237 974547338 80
2012-08-08 21:00:10 2012-08-08 21:00:28 6 2886828509 1111 3395507106 30179 2007493616 80
2012-08-08 21:00:25 2012-08-08 21:00:28 6 2886811814 1111 3395517743 34249 2072702869 80
2012-08-08 20:59:57 2012-08-08 21:00:28 6 2886780595 1111 3395507091 63169 1872834775 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886745283 1111 3395517711 38566 1863134645 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886852868 1111 3395507129 19216 989566331 80
2012-08-08 21:00:22 2012-08-08 21:00:28 6 2886758076 1111 3395517723 37910 3061190502 80
2012-08-08 21:00:22 2012-08-08 21:00:28 6 2886758076 1111 3395517723 37886 2079006794 80
2012-08-08 21:00:25 2012-08-08 21:00:28 6 2886788330 1111 3395507099 15078 460553383 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886756269 1111 3395517721 57538 2008813541 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886906371 1111 3395507148 65509 1884961048 80
2012-08-08 20:59:51 2012-08-08 21:00:28 6 2886893244 1111 3395517789 27585 2071802397 995
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886810351 1111 3395517742 10465 1971814472 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886908390 1111 3395507150 58599 3419418057 80
2012-08-08 21:00:11 2012-08-08 21:00:28 6 2886811967 1111 3395517743 43433 2099759129 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886908416 1111 3395507150 60161 1027056891 80
2012-08-08 21:00:24 2012-08-08 21:00:28 6 2886794472 1111 3395507104 63499 1872769542 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886859643 1111 3395507135 41589 1008470934 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886908926 1111 3395507151 26758 1027061456 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886844821 1111 3395507121 48598 989542829 80
2012-08-08 21:00:14 2012-08-08 21:00:28 6 2886811914 1111 3395517743 40207 2071819051 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886776231 1111 3395507087 57398 1027061476 80
2012-08-08 21:00:21 2012-08-08 21:00:28 6 2886895128 1111 3395507138 31084 1020918811 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886896369 1111 3395507139 41560 2071819499 80
2012-08-08 21:00:15 2012-08-08 21:00:28 6 2886866997 1111 3395517764 53220 1008528500 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886733364 1111 3395517700 27617 1850417510 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886763900 1111 3395507076 21749 2072679568 80
2012-08-08 21:00:24 2012-08-08 21:00:28 6 2886848688 1111 3395507125 24485 460553373 80
2012-08-08 20:59:50 2012-08-08 21:00:28 6 2886866792 1111 3395517764 40930 2072313366 80
2012-08-08 20:59:55 2012-08-08 21:00:28 6 2886917742 1111 3395507159 43536 2071873572 80
2012-08-08 20:59:55 2012-08-08 21:00:28 6 2886917742 1111 3395507159 43542 2071873572 80
2012-08-08 20:59:53 2012-08-08 21:00:28 6 2886801934 1111 3395517734 17623 2007483189 8080
2012-08-08 20:59:55 2012-08-08 21:00:28 6 2886917742 1111 3395507159 43537 2071873572 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886886283 1111 3395517782 58048 2071816694 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886735314 1111 3395517702 16591 2071799544 80
2012-08-08 20:59:55 2012-08-08 21:00:28 6 2886917742 1111 3395507159 43524 2071873572 80
2012-08-08 21:00:20 2012-08-08 21:00:28 6 2886849684 1111 3395507126 20262 2008825959 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886872604 1111 3395517770 5537 3419418056 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886853794 1111 3395507130 10753 2099722272 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886755008 1111 3395517720 45872 1883357744 80
2012-08-08 21:00:21 2012-08-08 21:00:28 6 2886895128 1111 3395507138 31121 2078933535 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886864839 1111 3395517762 51804 1850417452 80
2012-08-08 21:00:19 2012-08-08 21:00:28 6 2886858061 1111 3395507134 10700 2071819372 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886776231 1111 3395507087 57410 1027061476 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886858854 1111 3395507134 58306 1020914578 80
2012-08-08 21:00:21 2012-08-08 21:00:28 6 2886774805 1111 3395507086 35831 1883303354 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886794557 1111 3395507105 4593 3708103499 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886747135 1111 3395517713 21641 2099740446 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886863802 1111 3395517761 53630 1863145458 5224
2012-08-08 21:00:22 2012-08-08 21:00:28 6 2886911235 1111 3395507153 37254 2095615735 21
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886860043 1111 3395507136 1581 294986889 5223
2012-08-08 20:59:56 2012-08-08 21:00:28 6 2886780595 1111 3395507091 63161 1883302610 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886732547 1111 3395517699 42653 294986856 5223
2012-08-08 20:59:54 2012-08-08 21:00:28 6 2886734208 1111 3395517701 14230 2007484922 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886866964 1111 3395517764 51273 2072105082 80
2012-08-08 21:00:00 2012-08-08 21:00:28 6 2886780595 1111 3395507091 63144 1872834775 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886914262 1111 3395507156 26777 2072104968 80
2012-08-08 20:59:54 2012-08-08 21:00:28 6 2886734208 1111 3395517701 14273 2007484922 80
2012-08-08 21:00:25 2012-08-08 21:00:28 6 2886847997 1111 3395507124 47084 2021394494 80
2012-08-08 21:00:21 2012-08-08 21:00:28 6 2886785128 1111 3395507096 15002 294986849 5223
2012-08-08 21:00:25 2012-08-08 21:00:28 6 2886783177 1111 3395507094 26001 2072101596 443
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886735924 1111 3395517702 53178 1850417918 80
2012-08-08 21:00:09 2012-08-08 21:00:28 6 2886837532 1111 3395507114 59353 2071819198 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886891515 1111 3395517787 51880 1884983223 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886737305 1111 3395517704 8009 1872834975 443
2012-08-08 21:00:16 2012-08-08 21:00:28 6 2886755910 1111 3395517721 35947 2918544417 80
2012-08-08 21:00:27 2012-08-08 21:00:28 6 2886771117 1111 3395507083 6645 1884960474 80
2012-08-08 21:00:20 2012-08-08 21:00:28 6 2886785801 1111 3395507096 55430 2099718013 80
2012-08-08 21:00:24 2012-08-08 21:00:28 6 2886756061 1111 3395517721 45056 3419418065 80
2012-08-08 21:00:14 2012-08-08 21:00:28 6 2886771706 1111 3395507083 41990 1883302599 80
2012-08-08 20:59:55 2012-08-08 21:00:28 6 2886917742 1111 3395507159 43511 2071873572 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886853131 1111 3395507129 34983 296567345 443
2012-08-08 20:59:55 2012-08-08 21:00:28 6 2886917742 1111 3395507159 43538 2071873572 80
2012-08-08 21:00:23 2012-08-08 21:00:28 6 2886857519 1111 3395507133 42212 460553373 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886886465 1111 3395517783 4972 989566680 80
2012-08-08 21:00:25 2012-08-08 21:00:28 6 2886753976 1111 3395517719 47964 1884981528 80
2012-08-08 20:59:56 2012-08-08 21:00:28 6 2886809185 1111 3395517741 4537 2071872692 80
2012-08-08 21:00:26 2012-08-08 21:00:28 6 2886840353 1111 3395507117 36547 1027051331 80
2012-08-08 21:00:20 2012-08-08 21:00:28 6 2886840637 1111 3395507117 53634 1872832059 80
2012-08-08 21:00:19 2012-08-08 21:00:28 6 2886876032 1111 3395517773 19163 1884968518 80
2012-08-08 21:00:19 2012-08-08 21:00:28 6 2886876032 1111 3395517773 19158 1884968518 80
100 rows selected.
LS@LEO> select index_name,index_type,status from user_indexes where table_name='LEO_TEST_SQLLOAD3'; 我们创建主键已经失效
INDEX_NAME INDEX_TYPE STATUS
------------------------------ --------------------------- --------
PK_LEO_TEST_SQLLOAD3 NORMAL UNUSABLE
3.sqlload并行+直接加载存在索引的表，此时加载会失败，skip_index_maintenance=true参数可以跳过索引维护完成加载，此时索引状态unusable需要手工重建rebuild
create table leo_test_sqlload4 定义一个有主键的表
(
START_TIME date,
END_TIME date,
PROTOCOL varchar(20),
PRIVATE_IP varchar(20),
PRIVATE_PORT varchar(20) constraint pk_leo_test_sqlload4 primary key ,
SRC_IP varchar(20),
SRC_PORT varchar(20),
DEST_IP varchar(20),
DEST_PORT varchar(20)
);
sqlldr userid=ls/ls control=leo_test4.ctl data=leo_test1.data log=leo_test4.log direct=true parallel=true 并行+直接加载
SQL*Loader: Release 10.2.0.1.0 - Production on Thu Aug 9 16:19:25 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
SQL*Loader-951: Error calling once/load initialization 报错：加载初始化参数错误
ORA-26002: Table LS.LEO_TEST_SQLLOAD4 has index defined upon it. 表上有索引定义，所以加载会失败
LS@LEO> select index_name,index_type,status from user_indexes where table_name='LEO_TEST_SQLLOAD4';
INDEX_NAME INDEX_TYPE STATUS
------------------------------ --------------------------- --------
PK_LEO_TEST_SQLLOAD4 NORMAL VALID 现在索引还是有效的
sqlldr userid=ls/ls control=leo_test4.ctl data=leo_test1.data log=leo_test4.log direct=true parallel=true skip_index_maintenance=true;
SQL*Loader: Release 10.2.0.1.0 - Production on Thu Aug 9 16:30:52 2012
Copyright (c) 1982, 2005, Oracle. All rights reserved.
Load completed - logical record count 100. 使用skip_index_maintenance=true跳过索引维护，100行记录成功加载
LS@LEO> select count(*) from leo_test_sqlload4;
COUNT(*)
----------
100
LS@LEO> select index_name,index_type,status from user_indexes where table_name='LEO_TEST_SQLLOAD4';
INDEX_NAME INDEX_TYPE STATUS
------------------------------ --------------------------- --------
PK_LEO_TEST_SQLLOAD4 NORMAL UNUSABLE 加载后索引状态变成unusable需要手工重建rebuild
小结：我们在sqlload工具加载数据时一定要关注表上是否有索引，并且是什么类型的，正像世界万物一样，没有完美的工具，有得必有失，如果提高性能就会索引失效，如果要维护索引的完整性那么就会增加性能开销，我们要做的更加细心、严谨、谦虚，以不变应万变。
