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1.temporay table语法
a>:基于事务的临时的表空间
b>:基于session的临时表空间
Hints:创建一个临时表,是属于所有的用户,还是只属于当前创建的用户呢?明天试下....
b>:pctused
3.row Migration/row chaining
a>:row migration 如果该表的pctfree设置的比较小,当这个数据进行更新的时候,发现这个数据块已经没有足够的空间来存放当前的行,此时数据库必须寻找新的块来存放改行,并且把这行数据迁移到新的数据块.在先前的数据块中只保存一个指向新数据块的指针.从而导致数据库的性能下降.至少带来的double I/O
b>:row chaining 如果当一行的记录超过了256列或者是一行的记录特别大,数据库的一个数据块存储不小当前的数据,此时oracle会将行分成多个row pieces.这个时候当前行就会存储多个块的指针引用.此时就叫row chaining.一个都是因为数据块的大小过于小造成的.
4.表的重组织
a>:基于事务的临时的表空间
create global temporary table tableName on commit delete rows (id number,name varchar2(10))
b>:基于session的临时表空间
create global temporary table tableName on commit preserve rows (id number,name varchar2(10))
Hints:创建一个临时表,是属于所有的用户,还是只属于当前创建的用户呢?明天试下....
2.compute pctfree/pctused[只对手动管理方式有影响]a>:pctfree
(Average row size - Initial row size)*100/Average row size[通过表分析可以得到]
b>:pctused
100-pctfree-Average row size*100/Available data space
3.row Migration/row chaining
a>:row migration 如果该表的pctfree设置的比较小,当这个数据进行更新的时候,发现这个数据块已经没有足够的空间来存放当前的行,此时数据库必须寻找新的块来存放改行,并且把这行数据迁移到新的数据块.在先前的数据块中只保存一个指向新数据块的指针.从而导致数据库的性能下降.至少带来的double I/O
b>:row chaining 如果当一行的记录超过了256列或者是一行的记录特别大,数据库的一个数据块存储不小当前的数据,此时oracle会将行分成多个row pieces.这个时候当前行就会存储多个块的指针引用.此时就叫row chaining.一个都是因为数据块的大小过于小造成的.
4.表的重组织
--------命令 alter table tablename move tablespace newtabs --------查看表的详细结构(9i有bug) select dbms_metadata.get_ddl('对象的类型','对象的名字') ----删除表,cascade constrains 删除以张表作为主表的从表 drop table tablename cascade constraints -------使用unused选项 alter table tablename set unused colname; alter table tablename drop unused colname checkpoint 1000; alter table tablename drop columns continue checkpoint 1000; alter table tablename allocate extent;
发表评论
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Orale Auditing
2010-12-26 12:12 6141. 记录方式session/access 2. 标准审计 s ... -
管理权限
2010-12-26 10:49 6311.显示当前用户拥有的权限 select * from ses ... -
Management password & resource
2010-12-18 08:43 7041.profile 1>.failed_login_ ... -
Oracle logBuffer
2010-12-16 18:05 687各地现场的log_buffer都不一样,有的现场设置为200M ... -
Index Management
2010-12-12 11:11 7541.classification of indexex ... -
Undo Management
2010-12-11 10:53 6751.undo 表空间大小的确定 ... -
基于时间点的不完全恢复
2010-12-08 18:43 1536Hints: The requirements for dat ... -
oracle 热备份
2010-12-08 17:29 631SQL> set time on; 17:25 ... -
Oracle 冷备份
2010-12-07 11:34 536SQL> select count(*) fro ... -
Storage structure & Relationship
2010-12-05 09:35 7241.目标 a.描述数据库的逻辑结构 b.列出segment的类 ... -
Oracle 维护小技巧
2010-12-04 11:55 6021.重新编译有错误的函数,存储过程,包 select 'A ... -
oracle 性能监控常用SQL
2010-12-03 18:44 727监控数据库性能的SQL 查看tablespace的空間 ... -
Oracle正则表达式
2010-12-03 18:07 830Oracle 10g数据库内建了符合IEEE POSIX (P ... -
oracle 记录,嵌套表,集合
2010-12-03 11:39 16081.exists 检查集合中是否存在某个元素,collecti ... -
oracle 关联数组,bulk collect,forAll,动态SQL
2010-12-02 18:22 20171.今天花了点时间看了下plsql的关联数组,可谓是几经波折啊 ... -
手动创建数据库
2010-12-02 09:12 678[b]1.操作指南(摘自oracle在线帮助文档) Step ... -
Tablespaces&Datafiles
2010-12-01 21:32 659a.目标 1.定义表空间和数据文件,熟悉相关的脚本参数 2.创 ... -
Redo Log File
2010-11-30 21:00 799a.日志文件概要 1.Record all changes m ...
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