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row-level dependency tracking (10g new feature)SCN_TO_TIMESTAMP ora_rowscn SELECT ORA_ROWSCN,rowid from test;select SCN_TO_TIMESTAMP(205810284) from dual;refs:http://www.dbafan.com/blog/?p=194[@more@]

--测试总结：复合分区，有个很奇妙的地方，就是当数据插入到符合条件的第一个分区中。实现算法推测：对于按C1，C2两列进行复合分区的情况，插入时，首先判断是否小于C1，如果有匹配分区，则插入到符合条件的第一个分区中，否则如果插入的值=C1，则判断C2，如果有匹配分区，则插入到符合条件的第一个分区中。第二种理解：复合分区其实等同于单列分区，只是将多个列按二进制存放格式拼组在一起，组成一个单列字段。插入数据时，将分区字段值也按二进制存放格式拼组在一起进行单值判断。drop table pt1 ;create table pt1 (id1 number ,id2 n

cluster table :1, if one boundle can acrosss block ? no.2, if each member table exists in user_segments view ? Aso whether all member table take as an independent table ? answer: not exists.3, direct load performance poor ? yes, cluster table Not support direct load .4,[@more@]

refs:http://www.linuxidc.com/Linux/2011-04/34164.htm 经实验证实，确实如此，比较吃惊。test platform: windows 7 64bit with oracle 11.2.0.l 64bit.[@more@]

-- define a deferrable constraint allow check constraint when a transaction is commited, by default with immediate constraint allow check constraint after DML operation .-- allow primary key check deferrable.alter table t1 add constraint pk_t1 primary key (id) initially deferred ;insert into t1 (id) values (1) ;insert into t1 (id) values (1) ;commit ; -- report error here.-- allow foreign key check deferrable.alter table t2 add constraint fk_t2_t1 foreign key (dept_id) referencing t1initially de

logging mode of table has effective in performance of impdp utility.test scenario:table test has rows 480W .1, expdp scott/tiger directory=diskc dumpfile=outp1.dmp tables=test --470MB2, expdp scott/tiger directory=diskc dumpfile=outp2.dmp tables=test compression=all--160MB, use compression to reduce I/O with same or less time.1, table with logging .impdp scott/tiger directory=diskc dumpfile=outp1.dmp tables=test time costs: 108s, and there are many archived log produced. 2, table with nologging

-- create a hash partition table.-- And specify a default tablespace for partitioned table.create table obj_pt tablespace users -- see follwing comment <1>partition by (object_id)(partition p1 tablespace ts_1, partition p1 tablespace ts_2 ); -- add hash partition alter table obj_pt add partition p3 ;alter table obj_pt add partition p4 tablespace ts_1;-- something relation to transport tablespace.<1> if you did not specify default tablespace for a partition table. Then it's rely on d

Oracle Freelist和HWM原理及性能优化http://www.knowsky.com/385108.html[@more@]

ROWDEPENDENCIES:http://www.itpub.net/thread-982860-1-1.html# ORA_ROWSCNSQL> select rowid,ora_rowscn,a from t1;scn_to_timestamp(ora_rowscn) chg_time create table t_emp2 rowdependencies as select * from t_emp ;[@more@]

Oracle数据压缩http://blog.csdn.net/nhy520/archive/2008/11/05/3226519.aspx[@more@]

shrink space报ora-10635http://www.linuxgoo.com/html/database/2009-05/561.html表test为分区表，只有一分区(pmaxvalue)。表处于users表空间内，而分区pmaxvalue位于users2内.表空间users和users2均为ASSM。alter table test enable row movement后，执行alter table test shrink space却报ORA-10635: invalid segment or tablespace type为何会这样呢？要来表是compressed ，我把表改为nocompressed 就可以了shrink_clause解释 shrink_clause 允许手动地释放表、索引组织表、索引、分区、物化视图和物化视图日志的空间。这个语句只对自

alter table move跟shrink space的区别http://blog.csdn.net/wangdeng1314/archive/2010/07/15/5735768.aspx[@more@]