SUMMARY: Oracle 64 bits slower than 32 bits one under Solaris 8 6 4 bits kernel

From: DAUBIGNE Sebastien - BOR ( ) <>
Date: Thu Nov 13 2003 - 08:14:47 EST
Thanks for your answers. There is a general consensus. I will quote Neil's
answer :

"Actually, performance wise 32 bits is faster than 64 bits Oracle if it's
the same buffer size.  And normally the reason for going to 64 bits is if
you want to access more memory (max 4GB for 32 bits).  Thus you would need
to increase the SGA sizes if you want performance improvements in your 64
bit Oracle."

The problem is that Oracle already (before migrating to 64 bits) used a
large part of the physical memory (70%), but it was break into many (as we
use high parallelism) per-process private memory segments : SORT_AREA,

Hence, I can hardly increase the SGA without decreasing per-process private
memory (SORT/HASH).
The database is a large (1.5 Tb) DSS (Datawarehouse), with many read-only
and sequential (full-scan) access, so I doubt increasing the buffer cache
will help much.

But, I will give it a chance and increase the Oracle buffer cache to make
the SGA larger, from 2,5 Gb to, say, 5 Gb, and let you know.

Sebastien DAUBIGNE
<>  - (+33)
SchlumbergerSema - SGS/DWH/Pessac

-----Message d'origine-----
De:	DAUBIGNE Sebastien  - BOR ( )
Date:	vendredi 7 novembre 2003 16:12
Objet:	Oracle 64 bits slower than 32 bits one under Solaris 8 64 bits ke

Recently we upgraded our E6500 from Solaris 2.6/32 bits to Solaris 8/64

Then we migrated our Oracle RDBMS database (OLAP, DSS) from 32 bits
to 64 bits.

The problem is, we got such poor throughput with Oracle/64+Solaris 8/64
compared to Oracle/32+Solaris 2.6/32  that we had to go back to Oracle/32
(keeping Solaris 8/64) to get our original throughput.

As I couldn't see anything trivially (disk, CPU, memory) wrong on the
Solaris side during poor throughput, we are currently looking on the Oracle
side, but I wonder if you know any Solaris-related usual tips that can
explain why Oracle is slower in 64 bits than in 32 bits mode under Solaris 8
64 bits, as I've always believed that the 64 bits RDBMS would be kicker than
the 32 bits one.

Note : Oracle parameters (init.ora) are the same for both 32/64 (except
SHARE_POOL which was slightly increase for 64). We use raw-devices (so
nothing related to page caching).

Thanks in advance, I  will summarize.
Sebastien DAUBIGNE
<>  - (+33)
SchlumbergerSema - SGS/DWH/Pessac
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Received on Thu Nov 13 08:14:43 2003

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