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Re: Imported DB runs SLOWER on faster machine

From: Daniel Morgan <dmorgan_at_exesolutions.com>
Date: Mon, 22 Jul 2002 23:20:35 GMT
Message-ID: <3D3C9301.93124C13@exesolutions.com>


Rick Denoire wrote:

> Hello
>
> I just exported some schemas from an Oracle DB (8.1.7, Solaris) and
> imported them into a Test DB (Windows NT). Die PC is somewhat faster
> than the Sun Enterprise 3500 (although it has 4 CPUs , UltraSparc II,
> and a Raid), as I could confirm doing some tests without the DB.
>
> But some long running applications seem to never end on this PC. A job
> running about 4 min on the Sun system seems to run for DAYS not! I was
> able to determine that it definitely has something to do with I/O.
> Well, this PC has a cheap Promise controller and a Raid 0 system with
> 4 EIDE disks. As I said, using other applications and benchmarks
> proved that the system is really fast (Athon 2000+ MHz, 1.5 GB RAM,
> >50 MB/sec sustained transfer rate from the harddisks.
>
> Two possibilities:
> 1 - the data chunks read by Oracle mismatch the overall stripe size of
> the Raid 0 disks. Oracle always reads at least db_blocksize x
> db_file_multiblock_read_count. I could not find out the stripe
> parameters, because there was no chance to reboot the PC.
>
> 2 - Datafiles on the NT system are too large (>20GB). I just forgot
> that it is not Unix :-) Could anyone comment on maximum Oracle
> datafile size under Windows NT SP 6? But hey, the DB works somehow.
>
> Anyway, when the application runs, there is ALWAYS contention of type
> db_sequential_read, and as one updates the number of logical read
> blocks, it is possible to see how slow this operation works. The CPU
> is almost idle, contrary to the Raid.
>
> But I still know nothing about the real CAUSE of the problem. Could
> any one out there give me some hints about how to identify it?
>
> Thanks a lot
>
> Rick Denoire

I could add a lot of additional items to your list of two. All of which have to do with tuning. But the most glaring thing missing from your posting is that you didn't run DBMS_STATS to analyze tables and indexes. So, if that is the case, the CBO is just making wild guesses or out on vacation

Daniel Morgan Received on Mon Jul 22 2002 - 18:20:35 CDT

Original text of this message

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