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Does execution plan depend on Client / Client-platform ? [message #188649] Mon, 21 August 2006 02:23 Go to next message
power_logic@yahoo.com
Messages: 2
Registered: August 2006
Junior Member
Hello everybody !

It is a strange case I deal with now:
Given an Oracle 10g RAC, I execute one and the same SELECT-Statement against the same DB, using an SQLPlus on a Windows workstation, and another time on a Linux machine.

The result is always the same:
the execution plans are completely different, so that the Linux-query does not return back at all, while the Windows request returns immediately.

Could anybody give a hint, why and how does an execution plan depend on the certain client?

Thanks a lot in advance
Re: Does execution plan depend on Client / Client-platform ? [message #188660 is a reply to message #188649] Mon, 21 August 2006 02:39 Go to previous messageGo to next message
rleishman
Messages: 3724
Registered: October 2005
Location: Melbourne, Australia
Senior Member
That would be unusual. Just to be absolutely positive, the server is the same for both queries, right?

There are some session settings that can affect the plan.
eg.
ALTER SESSION SET OPTIMIZER_MODE=FIRST_ROWS;


It is possible that you are using a client that does exactly this (automatically, behind the scenes) so that it can display the first screen of results ASAP. If one client uses indexes and nested loops, and the other uses FTS and hash joins, then the one with indexes is probably setting the Optimizer Mode (Optimizer Goal in older versions).

Ross Leishman
Re: Does execution plan depend on Client / Client-platform ? [message #188685 is a reply to message #188660] Mon, 21 August 2006 03:39 Go to previous message
power_logic@yahoo.com
Messages: 2
Registered: August 2006
Junior Member
Thanks for your reply, Ross.

It is the same server, quite right.



I am going to check the default settings of the respective client, to find out whether the session settings relevant to
the execution plan (e.g. optimiser_xxx) are different depending
on platform.

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