Re: truncate a table with many extents

From: <DEEDSD_at_Nationwide.com>
Date: Fri, 7 May 2004 10:53:04 -0400
Message-ID: <OF7C7A465F.7D08A810-ON85256E8D.0051A162@lnotes-gw.ent.nwie.net>

I did a truncate on a table with 10,000 (8k) extents in a LMT on 9.2.0.4 on solaris, with 10046 level 8 trace enabled. I didn't see tsq$ - am I missing something?

                                                                                                                  
                          "Jonathan Lewis"                                                                        
                          <jonathan_at_jlcomp.demon.  T                                                              
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                          ts.org                   Subject:                                          Re: truncate 
                                                   a table with many extents                                      
                                                                                                                  
                                                                                                                  
                          05/06/2004 02:29 PM                                                                     
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                          oracle-l

I think this is one that probably requires testing for every platform and version of Oracle.

I've just run a quick test on 9.2.0.4 with 169 extents in an LMT Uniform sized.

The most significant difference is that the TRUNCATE updated tsq$ once per extent removed, DROP updated tsq$ once at the end. On the other hand, the DROP command triggered various other (mostly small) actions, including a call to a procedure called aw_drop_proc.

The most significant difference, though, was the handling of tsq$, and it made the truncate much more expensive in undo and redo.

Regards

Jonathan Lewis

http://www.jlcomp.demon.co.uk

http://www.jlcomp.demon.co.uk/faq/ind_faq.html The Co-operative Oracle Users' FAQ

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Original Message ----- From: "Riyaj Shamsudeen" <rshamsud_at_jcpenney.com> To: <oracle-l_at_freelists.org> Sent: Thursday, May 06, 2004 5:13 PM Subject: RE: truncate a table with many extents

I performed some testing on this few weeks ago. I couldn't measure the undo blocks due to implicit commits from DDLs. Redo size and redo entries were used instead. Oracle 8.1.7.4 64 bit on Solaris 8.

Dictionary managed: Table with 1001 extents 20000 rows 128k extent size Truncate : redo size :756k redo entries : 3031 Drop : redo size :569k redo entries : 2183
Locally managed : Same code as above, but this generated 1251 extents. 128k uniform sized LMT Truncate : redo size 1.46MB redo entries : 10,020 Drop : redo size 367K redo entries : 3,804

We decided to use LMTs with drop statements (of course, this table is accessed through a procedure so no grants issue). Surprisingly, # of recursive calls dropped from 15,110 to 307 between truncate and drop statements in case of LMT.

It would be nice to see what happens with more # of extents.. Will try that soon.

HTH
Thanks
Riyaj "Re-yas" Shamsudeen
Certified Oracle DBA

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Received on Fri May 07 2004 - 09:52:24 CDT