Re: Estimating HCC ratios

From: Pantheon Systems <pantheon.oracle_at_gmail.com>
Date: Wed, 28 Jun 2017 08:50:22 -0400
Message-Id: <5179333C-9ACE-4D69-BE42-8D4839A3DD83_at_gmail.com>



Ok.. Thanks Rajeev

I'll try that on my test bed

> On Jun 28, 2017, at 08:10, RajeevGM <rprabha01_at_gmail.com> wrote:
>
> Hi,
>
> Like other listers have already mentioned,
> you can get the compression ratio using
> dbms_compression..
>
> As regards its' effectiveness, for example
> you could query against the hcc compressed table, followed by that against v$sess* tables
> and compare the numbers to that of a non hcc compressed one ...
>
> Between the compression data captured from dbms_compression.get_compression_ratio
> and the above v$sess** tables, you should be able to determine how effective has hcc been
> in your environment.
>
> HTH,
> Rajeev
>
>

>> On Jun 28, 2017, at 7:45 AM, Pantheon Systems <pantheon.oracle_at_gmail.com> wrote:
>> 
>> Let me clarify 
>> 
>> If I hv HCC enabled right now, how do I tell how effective it is 
>> 
>> I.e : How well it's compressing the data to a similar set of data ( the same database ) that doesn't hv HCC-enabled 
>> 
>> 
>> 
>> 
>> 
>>> On Jun 27, 2017, at 21:06, Andy Klock <andy_at_oracledepot.com> wrote:
>>> 
>>>> On Tue, Jun 27, 2017 at 7:50 PM, Pantheon Systems <pantheon.oracle_at_gmail.com> wrote:
>>>> Folks
>>>> 
>>>> Is there a way to estimate HCC compression ratios?
>>>> 
>>>> I.e.. To what extent HCC is employed in the database ?
>>>> 
>>>> Or what percentage of tables are HCC compressed & their ratios & whether it is archive high / low and so on 
>>>> 
>>> 
>>> I'm not sure I exactly understand your question.  If you don't have a means to test actual compression, you can estimate compression ratios by sampling your data with DBMS_COMPRESSION.  How you employ it and what percentage of the tables use HCC in your database is really up to what your needs are. If your tables are bulk loaded and only SELECTed from then HCC may be great. If they are heavily DMLed then probably not so great.
>>> 
>>> Andy K

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Received on Wed Jun 28 2017 - 14:50:22 CEST

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