Re: Does oracle db serialize concurrent read-only SELECT ?

How many CPUs in the server, what sort of time-scale, what are you running the
multiple concurrent clients on, and how much data is your query returning from each row ?

There are lots of ways in which a simple test may be giving the wrong impression about concurrency.

--
Jonathan Lewis
Yet another Oracle-related web site:  http://www.jlcomp.demon.co.uk

Practical Oracle 8i:  Building Efficient Databases
Publishers:  Addison-Wesley

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Jung Tjong wrote in message <3ADCA291.28BB234_at_cisco.com>...


>Jonathan,

>

>The table I'm querying has only about 3000 records containing

>rows that have only about 15 int and string columns, totalling

>to about .5k bytes. I did a select on all rows, so now where clause.

>It's a very simple query.

>

>My test program takes only a few % of the cpu while running,

>and each of the spawned process / connection seems to take

>only 0.x % of the cpu.  I don't see any abnormal disk accesses.

>So I don't think it is straining the SUN ultra-60 server that I'm

>running this on.

>The same test on MySQL database took nearly the same

>time whether I run one query or multiple concurrent queries.

>

>Jung

>

>Jonathan Lewis wrote:

>

>> Oracle does not do anything to serialized

>> read-only queries - however you could get

>> this type of behaviour if you query were

>> CPU bound or I/O bound in the first place.

>>

>> Are you running a small volume query

>> to do the test, or are you (for example)

>> running a tablescan across a 256MB

>> table as the base query ?