Sunday, August 28, 2022
一, 常用到的设置环境参数的语句
设置SCOTT/TIGER的DEMO
运行@ORACLE_HOME/sqlplus/demo/demobld.sql (响应的demodrop.sql.是DROP SCOTT的脚本)
做一个登陆用的login.sql
define _editor=vi
set serveroutput on size 1000000 使DBMS_OUTPUT有效.
set trimspool on SPOOL不会以定长来控制,而是以空格来控制
set long 5000 LONG或CLOG 显示的长度
set linesize 100
set pagesize 9999 每9999行后打印HEAD
column plan_plus_exp format a80 autotrace后explain plan output的格式
column global_name new_value gname
set termout off
define gname=idle
column global_name new_value gname
select lower(user) || '@' || substr( global_name, 1,
decode( dot, 0, length(global_name), dot-1) ) global_name
from (select global_name, instr(global_name,'.') dot from global_name );
set sqlprompt '&gname> '
set termout on
set trimspool on; 去除重定向（spool）输出每行的拖尾空格，缺省为off
得到username@dbname的提示符. scott@WWMDB>
二, 常用到的DBA脚本
Runstats 比较两个作相同事情的方法的优劣点。本包统计三个值，一个是时间（不重要，由于手工运行，而且偏差较大），二，使用内存方面，三，LATCH。
开发人员经常在自己的PC上装DB,然后进行开发,这些脚本的目的就是让开发人员可以观察自己的SQL是如何运行的以及效率如何.
create or replace view stats
as select 'STAT...' || a.name name, b.value
from v$statname a, v$mystat b
where a.statistic# = b.statistic#
union all
select 'LATCH.' || name, gets
from v$latch;
create global temporary table run_stats
( runid varchar2(15),
name varchar2(80),
value int )
on commit preserve rows;
create or replace package runstats_pkg
as
procedure rs_start; --运行操作之前
procedure rs_middle; --运行第一个操作之后
procedure rs_stop( p_difference_threshold in number default 0 ); --结束 --p_difference_threshold 控制多大差别才予以输出。
end;
create or replace package body runstats_pkg
as
g_start number; --全局变量。
g_run1 number;
g_run2 number;
procedure rs_start --清空以前的统计信息
is
begin
delete from run_stats; ---清空
insert into run_stats
select 'before', stats.* from stats;
g_start := dbms_utility.get_time;
end;
procedure rs_middle --记录第一个SQL运行时间,STATISTIC,LATCH
is
begin
g_run1 := (dbms_utility.get_time-g_start);
insert into run_stats
select 'after 1', stats.* from stats;
g_start := dbms_utility.get_time;
end;
procedure rs_stop(p_difference_threshold in number default 0)
is
begin
g_run2 := (dbms_utility.get_time-g_start);
dbms_output.put_line
( 'Run1 ran in ' || g_run1 || ' hsecs' );
dbms_output.put_line
( 'Run2 ran in ' || g_run2 || ' hsecs' );
dbms_output.put_line
( 'run 1 ran in ' || round(g_run1/g_run2*100,2) ||
'% of the time' );
dbms_output.put_line( chr(9) );
insert into run_stats
select 'after 2', stats.* from stats;
dbms_output.put_line
( rpad( 'Name', 30 ) || lpad( 'Run1', 10 ) ||
lpad( 'Run2', 10 ) || lpad( 'Diff', 10 ) );
for x in
( select rpad( a.name, 30 ) ||
to_char( b.value-a.value, '9,999,999' ) ||
to_char( c.value-b.value, '9,999,999' ) ||
to_char( ( (c.value-b.value)-(b.value-a.value)), '9,999,999' ) data
from run_stats a, run_stats b, run_stats c
where a.name = b.name
and b.name = c.name
and a.runid = 'before'
and b.runid = 'after 1'
and c.runid = 'after 2'
and (c.value-a.value) > 0
and abs( (c.value-b.value) - (b.value-a.value) )
> p_difference_threshold
order by abs( (c.value-b.value)-(b.value-a.value))
) loop
dbms_output.put_line( x.data );
end loop;
dbms_output.put_line( chr(9) );
dbms_output.put_line
( 'Run1 latches total versus runs -- difference and pct' );
dbms_output.put_line
( lpad( 'Run1', 10 ) || lpad( 'Run2', 10 ) ||
lpad( 'Diff', 10 ) || lpad( 'Pct', 8 ) );
for x in
( select to_char( run1, '9,999,999' ) ||
to_char( run2, '9,999,999' ) ||
to_char( diff, '9,999,999' ) ||
to_char( round( run1/run2*100,2 ), '999.99' ) || '%' data
from ( select sum(b.value-a.value) run1, sum(c.value-b.value) run2,
sum( (c.value-b.value)-(b.value-a.value)) diff
from run_stats a, run_stats b, run_stats c
where a.name = b.name
and b.name = c.name
and a.runid = 'before'
and b.runid = 'after 1'
and c.runid = 'after 2'
and a.name like 'LATCH%'
)
) loop
dbms_output.put_line( x.data );
end loop;
end;
end;
/
测试
SQL> create table wwm as select * from all_objects where 1=2;
表已创建。
SQL> create table wwm2 as select * from all_objects where 1=2;
表已创建。
SQL> exec runstats_pkg.rs_start;
PL/SQL 过程已成功完成。
SQL> insert into wwm select * from all_objects;
已创建34750行。
SQL> exec runstats_pkg.rs_middle;
PL/SQL 过程已成功完成。
然后用第二种方法，一行一行地插入。
SQL> begin
2 for x in (select * from all_objects)
3 loop
4 insert into wwm2 values x;
5 end loop;
6 commit;
7 end;
8 /
---------------( create procedure p( ENAME in varchar2 )
as
begin
for x in ( select * from emp where ename = ENAME ) loop
Dbms_output.put_line( x.empno );
end loop;
end;
-----------------
SQL> exec runstats_pkg.rs_stop(1000000)
Run1 ran in 3558 hsecs
Run2 ran in 14263 hsecs
run 1 ran in 24.95% of the time
Name Run1 Run2 Diff
STAT...session pga memory 0 4,040,516 4,040,516
STAT...session pga memory max 0 4,064,632 4,064,632
STAT...session pga memory max 0 4,064,632 4,064,632
STAT...session pga memory 0 4,106,052 4,106,052
STAT...redo size 3,920,896########## 8,291,688
STAT...redo size 3,920,896########## 8,352,408
Run1 latches total versus runs -- difference and pct
Run1 Run2 Diff Pct
305,006 1,462,079 1,157,073 20.86%
三, Mystat 统计某操作之前和之后的变化。
Mystat.sql脚本捕捉初始值
set echo off
set verify off
column value new_val V
define S="&1"
输入 1 的值: redo size --可以输入不同的值来判断不同的指标
set autotrace off
select a.name, b.value
from v$statname a, v$mystat b
where a.statistic# = b.statistic#
and lower(a.name) like '%' || lower('&S')||'%'
/
NAME VALUE
-----------------------------
redo size 16408460
set echo on
中间做需要统计的操作。
1* update wwm set object_name=lower(object_name)
SQL> /
已更新34750行。
mystat2脚本报告异同点。
set echo off
set verify off
select a.name, b.value V, to_char(b.value-&V,'999,999,999,999') diff
from v$statname a, v$mystat b
where a.statistic# = b.statistic#
and lower(a.name) like '%' || lower('&S')||'%'
NAME V DIFF
------------------------------------
redo size 26028120 9,619,660
可以看到这次UPDATE产生了9,619,660 bytes of redo.
四, Show_space 统计SEGMENT的空间使用具体情况。
create or replace procedure show_space
( p_segname in varchar2, --SGEMENT的NAME
p_owner in varchar2 default user, --默任是当前用户
p_type in varchar2 default 'TABLE', --SEGMENT 的TYPE
p_partition in varchar2 default NULL ) --PARTITION的NAME
-- this procedure uses authid current user so it can query DBA_*
-- views using privileges from a ROLE, and so it can be installed
-- once per database, instead of once per user who wanted to use it
authid current_user
as
l_free_blks number;
l_total_blocks number;
l_total_bytes number;
l_unused_blocks number;
l_unused_bytes number;
l_LastUsedExtFileId number;
l_LastUsedExtBlockId number;
l_LAST_USED_BLOCK number;
l_segment_space_mgmt varchar2(255);
l_unformatted_blocks number;
l_unformatted_bytes number;
l_fs1_blocks number; l_fs1_bytes number;
l_fs2_blocks number; l_fs2_bytes number;
l_fs3_blocks number; l_fs3_bytes number;
l_fs4_blocks number; l_fs4_bytes number;
l_full_blocks number; l_full_bytes number;
-- inline procedure to print out numbers nicely formatted
-- with a simple label
procedure p( p_label in varchar2, p_num in number )
is
begin
dbms_output.put_line( rpad(p_label,40,'.') ||
to_char(p_num,'999,999,999,999') );
end;
begin
-- this query is executed dynamically in order to allow this procedure
-- to be created by a user who has access to DBA_SEGMENTS/TABLESPACES
-- via a role as is customary.
-- NOTE: at runtime, the invoker MUST have access to these two
-- views!
-- this query determines if the object is an ASSM object or not
begin
execute immediate
'select ts.segment_space_management
from dba_segments seg, dba_tablespaces ts
where seg.segment_name = :p_segname
and (:p_partition is null or
seg.partition_name = :p_partition)
and seg.owner = :p_owner
and seg.tablespace_name = ts.tablespace_name'
into l_segment_space_mgmt
using p_segname, p_partition, p_partition, p_owner;
exception
when too_many_rows then
dbms_output.put_line
( 'This must be a partitioned table, use p_partition => ');
return;
end;
-- if the object is in an ASSM tablespace, we must use this API
-- call to get space information, otherwise we use the FREE_BLOCKS
-- API for the user-managed segments
if l_segment_space_mgmt = 'AUTO'
then
dbms_space.space_usage
( p_owner, p_segname, p_type, l_unformatted_blocks,
l_unformatted_bytes, l_fs1_blocks, l_fs1_bytes,
l_fs2_blocks, l_fs2_bytes, l_fs3_blocks, l_fs3_bytes,
l_fs4_blocks, l_fs4_bytes, l_full_blocks, l_full_bytes, p_partition);
p( 'Unformatted Blocks ', l_unformatted_blocks );
p( 'FS1 Blocks (0-25) ', l_fs1_blocks );
p( 'FS2 Blocks (25-50) ', l_fs2_blocks );
p( 'FS3 Blocks (50-75) ', l_fs3_blocks );
p( 'FS4 Blocks (75-100)', l_fs4_blocks );
p( 'Full Blocks ', l_full_blocks );
else
dbms_space.free_blocks(
segment_owner => p_owner,
segment_name => p_segname,
segment_type => p_type,
freelist_group_id => 0,
free_blks => l_free_blks);
p( 'Free Blocks', l_free_blks );
end if;
-- and then the unused space API call to get the rest of the
-- information
dbms_space.unused_space
( segment_owner => p_owner,
segment_name => p_segname,
segment_type => p_type,
partition_name => p_partition,
total_blocks => l_total_blocks,
total_bytes => l_total_bytes,
unused_blocks => l_unused_blocks,
unused_bytes => l_unused_bytes,
LAST_USED_EXTENT_FILE_ID => l_LastUsedExtFileId,
LAST_USED_EXTENT_BLOCK_ID => l_LastUsedExtBlockId,
LAST_USED_BLOCK => l_LAST_USED_BLOCK );
p( 'Total Blocks', l_total_blocks );
p( 'Total Bytes', l_total_bytes );
p( 'Total MBytes', trunc(l_total_bytes/1024/1024) );
p( 'Unused Blocks', l_unused_blocks );
p( 'Unused Bytes', l_unused_bytes );
p( 'Last Used Ext FileId', l_LastUsedExtFileId );
p( 'Last Used Ext BlockId', l_LastUsedExtBlockId );
p( 'Last Used Block', l_LAST_USED_BLOCK );
end;
SQL> desc show_space
PROCEDURE show_space
参数名称 类型 输入/输出默认值?
------------------------------ ----------------------- ------ --------
P_SEGNAME VARCHAR2 IN
P_OWNER VARCHAR2 IN DEFAULT
P_TYPE VARCHAR2 IN DEFAULT
P_PARTITION VARCHAR2 IN DEFAULT
ASSM和user space managed tablespaces得到的结果不同,以下用user space managed tablespaces来说明
SQL> exec show_spacE('WWM');
Free Blocks............................. 2
Total Blocks............................ 5,120
Total Bytes............................. 41,943,040
Total MBytes............................ 40
Unused Blocks........................... 13
Unused Bytes............................ 106,496
Last Used Ext FileId.................... 1
Last Used Ext BlockId................... 46,473
Last Used Block......................... 115
FULL BLOCKS: full表示在没有变化之前不会再被分配出去。
Total Blocks, Total Bytes, Total MBytes: 整个分配给此SEGMENT的空间。
Unused Blocks, Unused Bytes:分配给SEGMENT，但是还没有使用，也就是说在HWM之上的空闲块。
Last Used Ext FileId: 最后一个extent所在的FILE ID.
Last Used Ext BlockId: 最后一个EXTENT 的BEGIN BLOCK ID.
FS1 Blocks–FS4 Blocks: 例如,0-25,表示在0-25%之间的空块.
做一个大表,以供测试使用
create table big_table
as
select rownum id, a.*
from all_objects a
where 1=0
/
alter table big_table nologging;
insert /*+ append */
into big_table
select rownum, a.*
from all_objects a;
已创建29645行。
1 insert /*+ append */
2 into big_table
3 select rownum+29646, a.*
4* from all_objects a
SQL> /
已创建29645行。
alter table big_table add constraint
big_table_pk primary key(id)
1 begin
2 dbms_stats.gather_table_stats
3 ( wnname => 'SYSTEM',
4 tabname => 'BIG_TABLE',
5 method_opt => 'for all indexed columns',
6 cascade => TRUE );
7* end;
五, 绑定变量与非绑定变量
阅读本章可以参考我的 BIND VARIABLE
http://sunmoonking.spaces.live.com/blog/cns!E3BD9CBED01777CA!175.entry
测试表
create table t ( x int );
绑定变量
create or replace procedure proc1
as
begin
for i in 1 .. 10000
loop
execute immediate
'insert into t values ( :x )' using i;
end loop;
end;
/
非绑定变量
create or replace procedure proc2
as
begin
for i in 1 .. 10000
loop
execute immediate
'insert into t values ( '||i||')';
end loop;
end;
/
SQL> exec runstats_pkg.rs_start;
PL/SQL 过程已成功完成。
SQL> exec proc1
PL/SQL 过程已成功完成。
SQL> exec runstats_pkg.rs_middle;
PL/SQL 过程已成功完成。
SQL> exec proc2
PL/SQL 过程已成功完成。
SQL> exec runstats_pkg.rs_stop(1000); --差别大于1000的才输出
Run1 ran in 1622 hsecs
Run2 ran in 4378 hsecs
run 1 ran in 37.05% of the time
Name Run1 Run2 Diff
STAT...bytes received via SQL* 387 1,690 1,303
STAT...bytes sent via SQL*Net 276 1,798 1,522
STAT...parse count (hard) 5 10,009 10,004
…………………………………………………………………………….
Run1 latches total versus runs -- difference and pct
Run1 Run2 Diff Pct
313,680 1,625,995 1,312,315 19.29%
PL/SQL 过程已成功完成。
可以看到PRO2基本上是PRO1的三倍,也就是说解析时间占完整运行完一条语句所耗时间的2/3，会多占用LATCH.可见,尽量减少硬解析能明显提高性能.
六,read-consistent
SQL> create table wwm as select * from all_users;
表已创建。
SQL> variable x refcursor
SQL> begin
2 open :x for select * from wwm;
3 end;
4 /
PL/SQL 过程已成功完成。
SQL> delete from wwm;
已删除27行。
SQL> commit;
提交完成。
SQL> print x
USERNAME USER_ID
------------------------------------------------------------ ----------
CREATED
--------------
BI 60
07-6月 -06
。。。。。。。。。。。。。。。
注意，这是在一个SESSION里做的实验。现建立一个表WWM，再OPEN一个CURSOR，再DELETE表WWM，甚至COMMIT之后还是可以PRINT CURSOR的原来的内容。
但是，需要明白的是，在OPEN一个CURSOR的时候并不取得数据或把数据放到某个地方；而是在DELETE的时候才将你需要的数据给你保留到一个地方（UNDO SEGMENT或叫ROLLBACK SEGMENT）。
七, flashback query.
SCN 是ORACLE内部时钟，
SQL> variable SCN number
SQL> exec :scn:=dbms_flashback.get_system_change_number
PL/SQL 过程已成功完成。
SQL> print scn
SCN
----------
1170636
SQL> select count(*) from wwm;
COUNT(*)
----------
0
SQL> desc wwm
名称 是否为空? 类型
----------------------------------------- -------- ----------------------------
USERNAME NOT NULL VARCHAR2(30)
USER_ID NOT NULL NUMBER
CREATED NOT NULL DATE
SQL> insert into wwm select * from all_users;
已创建27行。
SQL> select count(*) from wwm;
COUNT(*)
----------
27
SQL> select count(*) from wwm as of scn :scn;
COUNT(*)
----------
0
SQL> commit;
提交完成。
SQL> select count(*) from wwm as of scn :scn;
COUNT(*)
----------
0
甚至，我们可以用一个SQL得到两个SCN点的值
SQL> select * from (select count(*) from wwm),
2 (select count(*) from wwm as of scn :scn);
COUNT(*) COUNT(*)
---------- ----------
27 0
