Re: Things to consider during upgrade/migration
- From: "Gogala, Mladen" <gogala.mladen@xxxxxxxxx>
- To: loknath.73@xxxxxxxxx, Oracle L <oracle-l@xxxxxxxxxxxxx>
- Date: Sat, 13 Nov 2021 15:33:38 -0500
On 11/13/2021 1:46 PM, Lok P wrote:
Hello Listers, With respect to havinga safe upgrade(say from 11.2 to
19C) or migration(From HP to Exadata) experience with minimal
performance issues. Is there any guideline we should follow like
settingup exadata system stats in case the targetdatabase is going to
be exadata, Or verifying dictionary stats/table stats etc in a certain
way. Want to know experts' views, if there are any such guidelines?
The old Itanic-based HP is very different from Exadata, approximately as
much as Ford model T is different from Tesla model S. IT technology
development has happened at slightly faster pace than the automotive
technology development. Also, Oracle 19c is very different from Oracle
11g. Your thinking should start from the nature of your application. Is
that a data warehouse/reporting database type of application? Is it
OLTP? Is it mixed mode? Do you need a dedicated service with preferred
instance in case of an OLTP? Would mounting some instances in read
mostly mode benefit you in any way? Should you make use of heat maps?
You have that option with Exadata.
Exadata is primarily a data warehouse accelerator. Bloom filters on the
storage nodes are meant to increase the speed of the full table scan.
However, Exadata X8-2, the model that is mostly being sold these days,
has some very interesting features like RDMA (direct memory access over
the network) and persistent memory access, a form of extremely fast SSD
which can tremendously speed up commit processing. That would be very
important for an OLTP application. In other words, you will have to
re-tune your application all over again. To quote the late Yogi Berra,
"it's a deja vu all over again". The first thing to do is to get
acquainted with your new wonder of technology and learn what can it do.
Use fio or bonnie++ to measure IOPS. Use SLOB to see what Oracle can do
with that. After that start testing the application in earnest, always
having in mind that you might have to re-architect some pieces of it.
As far as system statistics is concerned, Oracle advises against that.
I once contacted Maria Colgan (aka "SQL Maria") directly with some
questions about that advice and she explained to me why is that the
official line. With Exadata, you will have Oracle Support on steroids.
They will extend any help that they can give on a very short notice.
They really do care about the Exadata customers.
Tel: (347) 321-1217
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