Oracle-L: Re: LOB tablespace

From: Tanel Poder <tanel.poder.003_at_mail.ee>
Date: Mon, 28 Jul 2003 15:29:24 -0800
Message-ID: <F001.005C7864.20030728152924@fatcity.com>

When storing lot's of LOBs id worry about:

whether in-line storage is allowed
PCTVERSION - for read consistency (LOBs do not use rollback segments for data pages, only )
CACHE - default is nocache, this requires always direct reads & writes which can hit IO. But if you do cache, this could kill your buffer cache, because LOB blocks read are placed to MRU (most recently used) end of LRU list (at least in 8i I believe it used to be that way).
LOGGING - can be disabled when using NOCACHE (direct writes). When logging is enabled with nocache, an update of data in LOB writes whole datablock images in redologs. If chunk size is set bigger than one block, then blocks of whole chunk are written to redo not depending on how much of LOB data was actually inserted.
CHUNK size - bigger chunks might be better performance wise (especially for growing objects), but if set too big, can waste space.
other less important issues, like lob index storage parameters...

So, there are lots of combinations.... For example if you don't have hardware write cache, the LOB direct writes might become bottleneck. And if you disable logging, you lose the ability to recover from media failure. If you use CACHE, there used to be problems with buffer cache. In 9i the alghoritms might have changed of course, but in 9i, there's additional nice feature: multiple block sizes and buffer pools - you can just keep your data in normal 8k block tablespaces, and LOBs in 16 or 32k block tablespaces.

Tanel.

Original Message ----- From: Indy Johal To: Multiple recipients of list ORACLE-L Sent: Tuesday, July 29, 2003 1:49 AM Subject: Re: LOB tablespace

Jared

This is not the case. I had imported a 150 Gig table containing LONG RAW column to BLOB with simple Export /Import sometime back last year and the only thing is that the column name given to BLOB column is same. This is export import from 81.7.3 non -partitioned table to 8.1.7.3 partitioned table

Indy Johal

       Jared.Still_at_radisys.com 
        Sent by: ml-errors_at_fatcity.com 
        07/28/03 06:34 PM 
        Please respond to ORACLE-L 

               
                To:        Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> 
                cc:         
                Subject:        Re: LOB tablespace

You won't be storing LOB's, you will be storing LONG's.

Oracle does not automatically convert LONG to LOB for you.

You will have to do that yourself ( check on MetaLink ) after you import the data.

Assuming that your new database will be using LMT's ( locally managed tablespaces ) I would think just set PCTFREE and PCTUSED to whatever you were using previously.

HTH Jared

  "Ehresmann, David" <David.Ehresmann_at_ps.net>   Sent by: ml-errors_at_fatcity.com
  07/28/2003 03:09 PM
  Please respond to ORACLE-L

         To:     Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
         cc: 
         Subject:        LOB tablespace

  I am going to import an Oracle 7 database into an Oracle 8.1.7.0.0   instance
  that I am going to make. I have 31 tables of which 11 hold LONG and/or   LONG
  RAW column datatypes. What storage clause should I put on the tablespace   to
  hold the LOBs most efficiently?

thanks,

David Ehresmann.

  --
  Please see the official ORACLE-L FAQ: http://www.orafaq.net   --
  Author: Ehresmann, David
   INET: David.Ehresmann_at_ps.net

  Fat City Network Services    -- 858-538-5051 http://www.fatcity.com
  San Diego, California        -- Mailing list and web hosting services
  ---------------------------------------------------------------------

To REMOVE yourself from this mailing list, send an E-Mail message to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).

  --
  Please see the official ORACLE-L FAQ: http://www.orafaq.net   --
  Author:
   INET: Jared.Still_at_radisys.com

  Fat City Network Services    -- 858-538-5051 http://www.fatcity.com
  San Diego, California        -- Mailing list and web hosting services
  ---------------------------------------------------------------------

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.net
-- 
Author: Tanel Poder
  INET: tanel.poder.003_at_mail.ee

Fat City Network Services    -- 858-538-5051 http://www.fatcity.com
San Diego, California        -- Mailing list and web hosting services
---------------------------------------------------------------------
To REMOVE yourself from this mailing list, send an E-Mail message
to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in
the message BODY, include a line containing: UNSUB ORACLE-L
(or the name of mailing list you want to be removed from).  You may
also send the HELP command for other information (like subscribing).

Received on Mon Jul 28 2003 - 18:29:24 CDT