Re: Undo Generation

  • From: "Jared Still" <jkstill@xxxxxxxxx>
  • To: oracle.tutorials@xxxxxxxxx
  • Date: Thu, 28 Jun 2007 12:09:02 -0700

On 6/28/07, DBA Deepak <oracle.tutorials@xxxxxxxxx> wrote:

Very simplified comments inline:

SQL> delete myemp;

14 rows deleted.

SQL> select used_ublk,used_urec from v$session s,v$transaction t where
s.taddr=t.addr and s.username='SCOTT';

 USED_UBLK  USED_UREC
---------- ----------
         2         14


Entire rows written to undo.

SQL> update myemp set sal=sal*1.1;

14 rows updated.

 USED_UBLK  USED_UREC
---------- ----------
         1          9


only updated column  (with rowid and overhead ) written to undo

SQL> insert into myemp select * from emp;

14 rows created.

 USED_UBLK  USED_UREC
---------- ----------
         1          1


Only rowid (with overhead) written to undo.


--
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist

Other related posts: