Oracle 12C 新特性 Temporary UNDO 临时回滚段

Oracle 12C 新特性 Temporary UNDO 可以减少存储在undo表空间的生成量和重做日志的生成

[oracle@db12c ~]$ sqlplus / as sysdbaSQL*Plus: Release 12.1.0.1.0 Production on Mon Apr 28 14:18:21 2014Copyright （c） 1982, 2013, Oracle. All rights reserved.
Connected to:
Oracle Database 12c Enterprise Edition Release 12.1.0.1.0 - 64bit Production
With the Partitioning, OLAP, Advanced Analytics and Real Application Testing options

SQL> create global temporary table test as select * from dba_objects where 1=0;Table created.SQL> alter session set temp_undo_enabled=false;Session altered.SQL> set autotrace traceonly statistics
SQL>
SQL> insert into test select * from dba_objects;19397 rows created.
Statistics
----------------------------------------------------------
83 recursive calls
1690 db block gets
2621 consistent gets
5 physical reads
121876 redo size
855 bytes sent via SQL*Net to client
842 bytes received via SQL*Net from client
3 SQL*Net roundtrips to/from client
3 sorts （memory）
0 sorts （disk）
19397 rows processedSQL> update test set object_name=lower（object_name）;19397 rows updated.
Statistics
----------------------------------------------------------
6 recursive calls
615 db block gets
375 consistent gets
0 physical reads
1310712 redo size
857 bytes sent via SQL*Net to client
846 bytes received via SQL*Net from client
3 SQL*Net roundtrips to/from client
1 sorts （memory）
0 sorts （disk）
19397 rows processedSQL> conn / as sysdba
Connected.
SQL> alter session set temp_undo_enabled=true
2 ;Session altered.SQL> set autotrace traceonly statistics
SQL>
SQL>
SQL> insert into test select * from dba_objects;19397 rows created.
Statistics
----------------------------------------------------------
5 recursive calls
1695 db block gets
2517 consistent gets
0 physical reads
280 redo size
844 bytes sent via SQL*Net to client
842 bytes received via SQL*Net from client
3 SQL*Net roundtrips to/from client
1 sorts （memory）
0 sorts （disk）
19397 rows processedSQL> update test set object_name=lower（object_name）;19397 rows updated.
Statistics
----------------------------------------------------------
2 recursive calls
22237 db block gets
827 consistent gets
0 physical reads
0 redo size
855 bytes sent via SQL*Net to client
846 bytes received via SQL*Net from client
3 SQL*Net roundtrips to/from client
1 sorts （memory）
0 sorts （disk）
19397 rows processedSQL>调整Oracle回滚的速度 http://www.linuxidc.com/Linux/2014-03/99098.htmOracle 回滚（ROLLBACK）和撤销（UNDO） http://www.linuxidc.com/Linux/2013-08/88792.htmOCP知识点讲解之 Undo回滚基础知识 http://www.linuxidc.com/Linux/2012-11/73949.htmOracle事务行级锁保存点回滚提交 http://www.linuxidc.com/Linux/2012-07/66120.htmOracle基本步骤前滚和回滚 http://www.linuxidc.com/Linux/2012-04/58727.htmOracle 回滚演示 rollback演示 http://www.linuxidc.com/Linux/2011-09/43833.htm更多Oracle相关信息见Oracle 专题页面 http://www.linuxidc.com/topicnews.aspx？tid=12本文永久更新链接地址