Re: 19C migration

Thanks a lot for your input.

Appreciate any other comments on the same.

On Sun, Dec 5, 2021 at 2:15 AM Lok P <loknath.73_at_gmail.com> wrote:

> Sorry , I don't have much idea. We are also slowly migrating the databases
> to 19C in our organization and in those, we have not changed any such
> application code etc so as to get benefit of any specific new feature. They
> were mainly in place migration for existing application code. But yes in
> one scenario we were trying to utilize private UNDO features to run a
> majority of our workload from DR/standby which was dependent on
> reading/writing to global temporary tables , which was not possible on
> 11.2.0.4. But , I do agree there are legends in this forum who have been
> playing with 19C since a long time, so they may guide you on any
> specific performance feature that you must try to get benefit, out of
> during this migration of critical databases.
>
> On Sat, Dec 4, 2021 at 2:35 AM Pap <oracle.developer35_at_gmail.com> wrote:
>
>> Thank You for the details.
>> Yes, as we are planning now, so if any new 19C feature will help us and
>> we need to do a few tweaks in application code we should be able to do
>> that. And I understand there is significant difference in the optimizer of
>> 19C and 11.2.0.4 and if there are any good things there in 19C, it must be
>> by default coming up with the default setup/parameters. But I was wondering
>> apart from defaults, if there was anything specific which we must do to get
>> the best of this 19C upgrade, mainly wrt performance. Any suggestions?
>>
>> On Fri, Dec 3, 2021 at 8:31 PM Lok P <loknath.73_at_gmail.com> wrote:
>>
>>> May not be the exact answer to your question. But as in your case it
>>> would be a version upgrade without any hardware upgrade, so you may get
>>> beaten severely by the plan changes. So as I had got the recommendation
>>> from many here in this forum , you should better turn on the baselining of
>>> all the existing plans (considering your ~150TB database may not have an
>>> exact test replica available to you) and appropriately capture/store those.
>>> That will help you atleast to get back to the original path just as a quick
>>> bandaid without impacting your customers much. And we have very bad
>>> experience with version 19.9 so hopefully you are going for the latest i.e
>>> 19.12. I am not sure if there are any features which we must use in 19C,
>>> others can comment on this, but do you say wrt application code you want
>>> to utilize new good features and if required, you are ready to plan to
>>> change your application code for that?
>>>
>>> On Fri, Dec 3, 2021 at 2:46 PM Pap <oracle.developer35_at_gmail.com> wrote:
>>>
>>>> Hello Listers, We have one of the big hybrid (catering to
>>>> Oltp+reporting type of workload) databases(~150TB in size) which is planned
>>>> to move from 11.2 to 19C. it's already on an X8-M high capacity exadata box.
>>>>
>>>> I understand with most of the databases now on 19C+ versions and with
>>>> many new features with this version as compared to 11.2.0.4, is there any
>>>> key learning we should follow or say are there any specific features we
>>>> must use or let our application code change to use to get best out of 19C
>>>> in this upgrade? May be related to optimization, compression etc.
>>>>
>>>

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