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Oracle 常用技巧和脚本

Jun 07, 2016 pm 05:53 PM
oracleCommonly used techniquesScript

1.如何查看ORACLE的隐含参数? ORACLE的显式参数,除了在INIT.ORA文件中定义的外,在svrmgrl中用"showparameter*",可以显示。但ORACLE还有一些参数是以“_”,开头的。如我们非常熟悉的“_offline_rollback_segments”等。 这些参数可在sys.x$ksppi表中查出

1. 如何查看ORACLE的隐含参数? 
ORACLE的显式参数,除了在INIT.ORA文件中定义的外,在svrmgrl中用"show parameter *",可以显示。但ORACLE还有一些参数是以“_”,开头的。如我们非常熟悉的“_offline_rollback_segments”等。 
这些参数可在sys.x$ksppi表中查出。 
语句:“select ksppinm from x$ksppi where substr(ksppinm,1,1)=’_’; ” 
2. 如何查看安装了哪些ORACLE组件? 
进入${ORACLE_HOME}/orainst/,运行./inspdver,显示安装组件和版本号。 
3. 如何查看ORACLE所占用共享内存的大小? 
可用UNIX命令“ipcs”查看共享内存的起始地址、信号量、消息队列。 
在svrmgrl下,用“oradebug ipc”,可看出ORACLE占用共享内存的分段和大小。 
example: 
SVRMGR> oradebug ipc 
-------------- Shared memory -------------- 
Seg Id Address Size 
1153 7fe000 784 
1154 800000 419430400 
1155 19800000 67108864 
4. 如何查看当前SQL*PLUS用户的sid和serial#? 
在SQL*PLUS下,运行: 
“select sid, serial#, status from v$session 
where audsid=userenv(’sessionid’);” 
5. 如何查看当前的字符集? 
在SQL*PLUS下,运行: 
“select userenv(’language’) from dual;” 
或: 
“select userenv(’lang’) from dual;” 
6. 如何查看数据库中某用户,正在运行什么SQL语句? 
根据MACHINE、USERNAME或SID、SERIAL#,连接表V$SESSION和V$SQLTEXT,可查出。 
SQL*PLUS语句: 
“SELECT SQL_TEXT FROM V$SQL_TEXT T, V$SESSION S WHERE T.ADDRESS=S.SQL_ADDRESS 
AND T.HASH_VALUE=S.SQL_HASH_VALUE 
AND S.MACHINE=’XXXXX’ OR USERNAME=’XXXXX’ -- 查看某主机名,或用户名 
/” 
7. 如何删除表中的重复记录? 
例句: 
DELETE 
FROM table_name a 
WHERE rowid > ( SELECT min(rowid) 
FROM table_name b 
WHERE b.pk_column_1 = a.pk_column_1 
and b.pk_column_2 = a.pk_column_2 ); 
8. 手工临时强制改变字符集 
以sys或system登录系统,sql*plus运行:“create database character set us7ascii;". 
有以下错误提示: 
* create database character set US7ASCII 
ERROR at line 1: 
ORA-01031: insufficient privileges 
实际上,看v$nls_parameters,字符集已更改成功。但重启数据库后,数据库字符集又变回原来的了。 
该命令可用于临时的不同字符集服务器之间数据倒换之用。 
9. 怎样查询每个instance分配的PCM锁的数目 
用以下命令: 
select count(*) "Number of hashed PCM locks" from v$lock_element where bitand(flags,4)0 

select count(*) "Number of fine grain PCM locks" from v$lock_element 
where bitand(flags,4)=0 

10. 怎么判断当前正在使用何种SQL优化方式? 
用explain plan产生EXPLAIN PLAN,检查PLAN_TABLE中ID=0的POSITION列的值。 
e.g. 
select decode(nvl(position,-1),-1,’RBO’,1,’CBO’) from plan_table where id=0 

11. 做EXPORT时,能否将DUMP文件分成多个? 
ORACLE8I中EXP增加了一个参数FILESIZE,可将一个文件分成多个: 
EXP SCOTT/TIGER FILE=(ORDER_1.DMP,ORDER_2.DMP,ORDER_3.DMP) FILESIZE=1G TABLES=ORDER; 
其他版本的ORACLE在UNIX下可利用管道和split分割: 
mknod pipe p 
split -b 2048m pipe order & #将文件分割成,每个2GB大小的,以order为前缀的文件: 
#orderaa,orderab,orderac,... 并将该进程放在后台。 
EXP SCOTT/TIGER FILE=pipe tables=order
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