RE: Performance of multi datafile tablespaces

Hi Bruce,

Manual striping is great for parallel query. See "Disk Configuration for Parallel Table Scans" at
http://www.ixora.com.au/tips/creation/parallel_table_scans.htm for why.

The RevealNet tip is probably motivated by a desire to avoid read/write lock contention. Temporary tablespace datafiles are particularly prone to this because of direct writes. See
http://www.ixora.com.au/tips/creation/raw_datafiles.htm for more on read/write locks.

@ Regards,
@ Steve Adams
@ http://www.ixora.com.au/
@ http://www.christianity.net.au/

-----Original Message-----
[mailto:Bruce.Reardon_at_comalco.riotinto.com.au] Sent: Thursday, 3 May 2001 15:55
To: Multiple recipients of list ORACLE-L

Hi,

We have a number of large tables that we want to increase the performance of queries against.

This will be using 8171 on NT utilising the Parallel query option (PQO) on a server with 4 CPUs.

Ideally we would like to partition the tables but due to the cost of the partitioning option (hundreds of thousands of dollars across our 3 sites) we have all but ruled this out for the moment.

So, what is being considered is manual striping of datafiles within tablespaces.

That is, each tablespace will consist of multiple datafiles (4 is being considered) with each datafile on separate hardware mirror sets. Locally Managed Tablespaces (LMTs) will also be used.

I am interested in feedback on this option - eg past experiences, comments, other alternatives etc.

Also, do you know of any references / whitepapers on this topic?

So far I have found the following:
http://www.revealnet.com/newsletter/disk_io_distribution.doc which suggests "Physically stripe the temporary tablespace across multiple disks by allocating multiple datafiles with sizes mapped to the tablespace's extent size (so each datafile contains exactly one extent)."

Metalink articles suggesting using minextent clause on tables / indexes and the need to ensure that the objects don't fit into just 1 extent - or in our case that the objects will require at least 4 extents.

Chapter 20 of the Oracle8i Designing and Tuning for Performance manual (8.1.7) under Striping Disks Manually.
and such commands as "ALTER TABLE ... ALLOCATE EXTENT DATAFILE '...' " but the manual reference only refers to when the datafiles are filled by 1 object.

Thanks,
Bruce Reardon
mailto:bruce.reardon_at_comalco.riotinto.com.au

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