Re: Undo Generation

On 6/28/07, DBA Deepak <oracle.tutorials_at_gmail.com> 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

--
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