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oracle常用傻瓜問題1000問(之四)
作者: ccbzzp
大家在應用oracle的時候可能會遇到很多看起來不難的問題, 特別對新手來說, 今天我簡單把它總結一下, 發布給大家, 希望對大家有幫助! 和大家一起探討, 共同進步!
對oracle高手來說是不用看的.
虚擬字段
133. currval 和 nextval
为表创建序列
create sequence empseq … ;
select empseq.currval from dual ;
自动插入序列的数值
insert into emp
values (empseq.nextval, lewis, clerk,
7902, sysdate, 1200, null, 20) ;
134. rownum
按设定排序的行的序号
select * from emp where rownum < 10 ;
135. rowid
返回行的物理地址
select rowid, ename from emp where deptno = 20 ;
136. 将n秒转换为时分秒格式？
set serverout on
declare
n number := 1000000;
ret varchar2(100);
begin
ret := trunc(n/3600) || 小时 || to_char(to_date(mod(n,3600),sssss),fmmi”分 “ss”秒”) ;
dbms_output.put_line(ret);
end;
137. 如何查询做比较大的排序的进程？
select b.tablespace, b.segfile#, b.segblk#, b.blocks, a.sid, a.serial#,
a.username, a.osuser, a.status
from v$session a,v$sort_usage b
where a.saddr = b.session_addr
order by b.tablespace, b.segfile#, b.segblk#, b.blocks ;
138. 如何查询做比较大的排序的进程的sql语句？
select /*+ ordered */ sql_text from v$sqltext a
where a.hash_value = (
select sql_hash_value from v$session b
where b.sid = &sid and b.serial# = &serial)
order by piece asc ;
139. 如何查找重复记录？
select * from table_name
where rowid!=(select max(rowid) from table_name d
where table_name.col1=d.col1 and table_name.col2=d.col2);
140. 如何删除重复记录？
delete from table_name
where rowid!=(select max(rowid) from table_name d
where table_name.col1=d.col1 and table_name.col2=d.col2);
141. 如何快速编译所有视图？
sql >spool view1.sql
sql >select ‘alter view ‘||tname||’
compile;’ from tab;
sql >spool off
然后执行view1.sql即可。
sql >@view1.sql;
142. ora-01555 snapshot too old的解决办法
增加minextents的值，增加区的大小，设置一个高的optimal值。
143. 事务要求的回滚段空间不够，表现为表空间用满（ora-01560错误），回滚段扩展到达参数 maxextents的值（ora-01628）的解决办法.
向回滚段表空间添加文件或使已有的文件变大；增加maxextents的值。
144. 如何加密oracle的存储过程？
下列存储过程内容放在aa.sql文件中
create or replace procedure testccb(i in number) as
begin
dbms_output.put_line(输入参数是||to_char(i));
end;
sql>wrap iname=a.sql;
pl/sql wrapper: release 8.1.7.0.0 – production on tue nov 27 22:26:48 2001
copyright (c) oracle corporation 1993, 2000. all rights reserved.
processing aa.sql to aa.plb
运行aa.plb
sql> @aa.plb ;
145. 如何监控事例的等待？
select event,sum(decode(wait_time,0,0,1)) “prev”,
sum(decode(wait_time,0,1,0)) “curr”,count(*) “tot”
from v$session_wait
group by event order by 4;
146. 如何回滚段的争用情况？
select name, waits, gets, waits/gets “ratio”
from v$rollstat c, v$rollname d
where c.usn = d.usn;
147. 如何监控表空间的 i/o 比例？
select b.tablespace_name name,b.file_name “file”,a.phyrds pyr,
a.phyblkrd pbr,a.phywrts pyw, a.phyblkwrt pbw
from v$filestat a, dba_data_files b
where a.file# = b.file_id
order by b.tablespace_name;
148. 如何监控文件系统的 i/o 比例？
select substr(c.file#,1,2) “#”, substr(c.name,1,30) “name”,
c.status, c.bytes, d.phyrds, d.phywrts
from v$datafile c, v$filestat d
where c.file# = d.file#;
149. 如何在某个用户下找所有的索引？
select user_indexes.table_name, user_indexes.index_name,uniqueness, column_name
from user_ind_columns, user_indexes
where user_ind_columns.index_name = user_indexes.index_name
and user_ind_columns.table_name = user_indexes.table_name
order by user_indexes.table_type, user_indexes.table_name,
user_indexes.index_name, column_position;
150. 如何监控 sga 的命中率？
select a.value + b.value “logical_reads”, c.value “phys_reads”,
round(100 * ((a.value+b.value)-c.value) / (a.value+b.value)) “buffer hit ratio”
from v$sysstat a, v$sysstat b, v$sysstat c
where a.statistic# = 38 and b.statistic# = 39
and c.statistic# = 40;
151. 如何监控 sga 中字典缓冲区的命中率？
select parameter, gets,getmisses , getmisses/(gets+getmisses)*100 “miss ratio”,
(1-(sum(getmisses)/ (sum(gets)+sum(getmisses))))*100 “hit ratio”
from v$rowcache
where gets+getmisses <>0
group by parameter, gets, getmisses;
152. 如何监控 sga 中共享缓存区的命中率，应该小于1% ？
select sum(pins) “total pins”, sum(reloads) “total reloads”,
sum(reloads)/sum(pins) *100 libcache
from v$librarycache;
select sum(pinhits-reloads)/sum(pins) “hit radio”,sum(reloads)/sum(pins) “reload percent”
from v$librarycache;
153. 如何显示所有数据库对象的类别和大小？
select count(name) num_instances ,type ,sum(source_size) source_size ,
sum(parsed_size) parsed_size ,sum(code_size) code_size ,sum(error_size) error_size,
sum(source_size) +sum(parsed_size) +sum(code_size) +sum(error_size) size_required
from dba_object_size
group by type order by 2;
154. 监控 sga 中重做日志缓存区的命中率，应该小于1%
select name, gets, misses, immediate_gets, immediate_misses,
decode(gets,0,0,misses/gets*100) ratio1,
decode(immediate_gets+immediate_misses,0,0,
immediate_misses/(immediate_gets+immediate_misses)*100) ratio2
from v$latch where name in (redo allocation, redo copy);
155. 监控内存和硬盘的排序比率，最好使它小于 .10，增加 sort_area_size
select name, value from v$sysstat where name in (sorts (memory), sorts (disk));
156. 如何监控当前数据库谁在运行什么sql语句？
select osuser, username, sql_text from v$session a, v$sqltext b
where a.sql_address =b.address order by address, piece;
157. 如何监控字典缓冲区？
select (sum(pins – reloads)) / sum(pins) “lib cache” from v$librarycache;
select (sum(gets – getmisses – usage – fixed)) / sum(gets) “row cache” from v$rowcache;
select sum(pins) “executions”, sum(reloads) “cache misses while executing” from v$librarycache;
后者除以前者,此比率小于1%,接近0%为好。
select sum(gets) “dictionary gets”,sum(getmisses) “dictionary cache get misses”
from v$rowcache
158. 监控 mts
select busy/(busy+idle) “shared servers busy” from v$dispatcher;
此值大于0.5时，参数需加大
select sum(wait)/sum(totalq) “dispatcher waits” from v$queue where type=dispatcher;
select count(*) from v$dispatcher;
select servers_highwater from v$mts;
servers_highwater接近mts_max_servers时，参数需加大
159. 如何知道当前用户的id号?
sql>show user;
or
sql>select user from dual;
160. 如何查看碎片程度高的表?
select segment_name table_name , count(*) extents
from dba_segments where owner not in (sys, system) group by segment_name
having count(*) = (select max( count(*) ) from dba_segments group by segment_name);
162. 如何知道表在表空间中的存储情况?
select segment_name,sum(bytes),count(*) ext_quan from dba_extents where
tablespace_name=&tablespace_name and segment_type=table group by tablespace_name,segment_name;
163. 如何知道索引在表空间中的存储情况?
select segment_name,count(*) from dba_extents where segment_type=index and owner=&owner
group by segment_name;
164、如何知道使用cpu多的用户session?
11是cpu used by this session
select a.sid,spid,status,substr(a.program,1,40) prog,a.terminal,osuser,value/60/100 value
from v$session a,v$process b,v$sesstat c
where c.statistic#=11 and c.sid=a.sid and a.paddr=b.addr order by value desc;
165. 如何知道监听器日志文件?
以8i为例
$oracle_home/network/log/listener.log
166. 如何知道监听器参数文件?
以8i为例
$oracle_home/network/admin/listener.ora
167. 如何知道tns 连接文件?
以8i为例
$oracle_home/network/admin/tnsnames.ora
168. 如何知道sql*net 环境文件?
以8i为例
$oracle_home/network/admin/sqlnet.ora
169. 如何知道警告日志文件?
以8i为例
$oracle_home/admin/sid/bdump/sidalrt.log
170. 如何知道基本结构?
以8i为例
$oracle_home/rdbms/admin/standard.sql
171. 如何知道建立数据字典视图?
以8i为例
$oracle_home/rdbms/admin/catalog.sql
172. 如何知道建立审计用数据字典视图?
以8i为例
$oracle_home/rdbms/admin/cataudit.sql
173. 如何知道建立快照用数据字典视图?
以8i为例
$oracle_home/rdbms/admin/catsnap.sql
待续…
