Re: Memory operations on Sun/Oracle M class servers vs T class servers

From: Stefan Koehler <>
Date: Wed, 17 Dec 2014 11:12:50 +0100 (CET)
Message-ID: <>

Hi Finn,
in addition to Tanel's awesome reply.

The current SCN is assigned to the cursor in the EXEC phase as well, which results in (fixed) SGA memory access (variable kcsgscn_) for each EXEC call.

P.S.: I stumbled across this M- and T-series stuff round about one year ago as well, while doing a database migration from Sun Solaris (SPARC) to Sun Solaris (x86) as the production was running on T-series and the export was much much slower. I was told (as i am not very familiar with the SUN CPU architecture) that the T-series was not designed for single thread performance, but for short parallel requests like a typical load with web sites. This description is covered now by Tanel's great CPU explanation.

Best Regards
Stefan Koehler

Oracle performance consultant and researcher Homepage:
Twitter: _at_OracleSK

> Tanel Poder <> hat am 17. Dezember 2014 um 03:55 geschrieben:
> And reading your original email all the way to the end - depending on the exec plan the FETCH part may be the easy part - EXEC for example needs to
> pin the cursor, put binds in place in memory, walks through the execution plan "initializes" various row sources that may mean memory allocation
> (but for SELECTs, the actual plan execution and row production starts in FETCH)...
> So, can't assume that EXEC is less memory intensive than a 4 logical IO-doing fetch that follows it.
> Tanel

Received on Wed Dec 17 2014 - 11:12:50 CET

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