Degree of parallelism and number of files in tablespace

Hi,
I am trying to find out the relationship between the number of files in a tablespace and degree of parallelism. does number of files in a tablespace effect dop in parallel query. because if more files are in the tablespace so the IO of the system has increased and system has become more feverable for parallel query.
However i looked into the formulas for calculating dop i dont find any parameter which specify how many file are there in a tablespace. please give me the formula of calculting dop in oracle.
regards
Nick

Maurice Muller wrote:
Did you run this test on an Exadata Storage Server? How much IO throughput did you have per process? No. That one is from a RAC cluster of DL580 G5s. There were 7 in that query, but I had 8 total. One was down at the time due to hardware failure.
The >500 DOP is from a RAC cluster of 16 DL580s (so DOP=512) to be exact.
The amount of I/O you get per slave (or talking aggregate) is dependent on what the query execution plan is. Simple things like select count(*) are very I/O intensive, but not very CPU/memory intensive. The blocks are read, counted and then discarded. A group by or hash join will be more CPU intensive and less I/O intensive. Over the course of a given query execution the use of resources will generally alternate. Heavy on I/O at first, then more CPU heavy for a hash join, etc.
How much IO throughput do you recommend per CPU(Core) for an Oracle DWH server?As a rule of thumb I size systems to have around 100MB/s of physical I/O throughput per CPU core. So for a four socket quad core DL580 G5 (16 cores) target 1600MB/s, which works out nicely to four 4Gbps FCP ports. Do note if you are using compression you will be delivering a logical I/O rate higher than the physical based on the compression ratio for the data.
With Exadata, things are a little different. Since the CPUs that do the physical I/O are not at the DB layer, no wait I/O shows up in the metrics. The db blocks are transferred to the host using iDB protocol, not FCP like most external storage.
For instance, here is a screen capture of a HP Oracle Database Machine running a single query that uses PQ
http://structureddata.org/files/life_without_waitio.png
The problem is that most storage system are, from my point of view, much to slow compared to the available CPUs performance. In most cases people don't realise that the IO throughput required for large parallel queries is not comparable with the one required for an OLTP system having >90% cache hit ratio.Very true. Also discussed here:
http://download.oracle.com/docs/cd/B28359_01/server.111/b28313/hardware.htm
Regards,
Greg Rahn
http://structureddata.org

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