ORACLE数据库使用的常见问题(四)

61. 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);

62. 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);

63. 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。
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。

64. 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;

65. 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;

66. 如何监控回滚段的争用情况?
select name, waits, gets, waits/gets “Ratio”
from v$rollstat C, v$rollname D
where C.usn = D.usn;

67. 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;

68. 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#;

69. 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;

70. 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;

71. 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;

72. 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;

73. 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’);

74. 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)’);

75. 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;

76. 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

77. 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

78. 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);

79. 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

80. 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;

81、如何知道使用CPU多的用户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;



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