Oracle 12C 新特性 Temporary UNDO 临时回滚段

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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

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oracle 12c 新特性 temporary undo 临时回滚段

[日期：2014-05-23] 来源：Linux社区作者：paulyibinyi [字体：]

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 sysdba

SQL*Plus: Release 12.1.0.1.0 Production on Mon Apr 28 14:18:21 2014

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.

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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 processed

SQL> 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 processed

SQL> 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 processed

SQL> 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 processed

SQL>

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