Re: 19C migration

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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