Oracle Database 12c In-Memory Feature – Part III. Enabled, Used or Confused? Don’t Be.

Index of Related Posts

This is part 3 in a series: Part I, Part II, Part III, Part IV, Part V.

Update: Oracle Acknowledges Software Defect

During the development of this study, Oracle’s Product Manager in charge of the In-Memory feature has cited Bug #19308780 as it relates to my findings. I need to point out, however, that it wasn’t until this blog installment that the defective functionality was acknowledged as a bug. Further, the bug being cited is not visible to customers so there is no closure. How can one have closure without knowing what, specifically, is acknowledged as defective? Also read more at The Register: Click here.

Other Blog Updates

Please note, there are blog updates at the end of this post.

 

Enabled By Default. Not Usable By Default.

It was my intention to only write 2 installments on my short series about Oracle Database 12c In-Memory Column Store feature usage. My hopes were quickly dashed when the following developments occurred:

1. A quote from an Oracle spokesman cited on informationweek.com was pulled because (I assume) it corroborated my assertion that the feature is enabled by default. It is, enabled by default.

Citations: Tweet about the quote, link to the July 26, 2014 version of the Informationweek.com article showing the Oracle spokesman quote: Informationweek.com 26 July 2014.

The July 26, 2014 version of the Informationweek.com article quoted an Oracle spokesman as having said the following:

Yes, Oracle Database In-Memory is an option and it is on by default, as have been all new options since Oracle Database 11g

2. An email from an Oracle Product Manager appeared on the oracle-l email list and stated the following:

So, it is explicitly NOT TRUE that Database In-Memory is enabled by default – and it’s (IMHO) irresponsible (at best) to suggest otherwise

Citation: link to the oracle-l list server copy of the email, screenshot of the email.

 

Features or Options, Enabled or Used

I stated in Part I that I think the In-Memory Column Store feature is a part of a hugely-important release.  But, since the topic is so utterly confusing I have to make some points.

It turns out that neither of the Oracle folks I mention above are correct. Please allow me to explain. Yes, the Oracle spokesman spoke the truth originally to Informationweek.com as reported by Doug Henschen. The truth that was spoken is, yes indeed, the In-Memory Column Store feature/option  is enabled by default. Now don’t be confused. There is a difference between enabled and usable and  in-use.

In Part II of the series I showed an example of the things that need to be done to put the feature into use–and remember, you’re not charged for it until it is used. I believe that post made it quite clear that there is a difference between enabled and in-use. What does the Oracle documentation say about In-Memory Column Store feature/option default settings? It says it is enabled by default. Full stop. Citation: Top-level initialization parameter enabled by default. I’ve put a screenshot of that documentation here for education sake:

enable-by-default

 

This citation of the documentation means the Oracle spokesman was correct.  The feature is enabled by default.

The problem is with the mixing of the words enabled and “use” in the documentation.

Please consider the following screenshot of a session where the top-level INMEMORY_QUERY parameter is set to the default (ENABLE) as well as the INMEMORY_SIZE parameter to grant some RAM to the In-Memory Column Store feature. In the screenshot you’ll see that I didn’t trigger usage of the feature just by enabling it. I did, however, show that you don’t have to “use” the feature to trigger “usage” so please visit Part II on that matter.

img1-mu

So here we sit with wars over words.

Oracle’s Maria Colgan just posted a helpful blog (or, practically a Documentation addendum) going over the initialization parameters needed to fully, really-truly enable the feature–or more correctly how to go beyond enabled to usable.  I’ve shown that Oracle’s spokesman was correct in stating the feature is enabled by default (INMEMORY_QUERY enabled by default). Maria and others showed that you have to set 2 parameters to really, truly, gosh-darnit use the feature that is clearly ENABLE(d) by default. I showed you that enabling the feature doesn’t mean you use the feature (as per the DBA_FEATURE_USAGE_STATICS view). I also showed you in Part II how one can easily, accidentally use the feature.  And using the feature is chargeable and that’s why I assert INMEMORY_QUERY should ship with the default value of DISABLE. It is less confusing and it maps well to prior art such as the handling of Real Application Clusters.

Trying To Get To A Summary

So how does one summarize all of this?  I see it as quite simple. Oracle could have shipped Oracle Database 12c 12.1.0.2 with the sole,  top-level enabling parameter disabled (e.g., INMEMORY_QUERY=DISABLE). Doing so would be crystal clear because it nearly maps to a trite sentence–the feature is DISABLE(d). Instead we have other involved parameters that are not top level adding to the confusion. And confusion indeed since the Oracle documentation insinuates INMEMORY_SIZE is treated differently when Automatic Memory Management is in play:

amm-issue

Prior Art

And what is that prior art on the matter? Well, consider Oracle’s (presumably) most profitable separately-licensed feature of all time–Real Application Clusters. How does Oracle treat this desirable feature? It treats it with a crystal-clear top-level, nuance-free disabled state:

cluster_database_default

So, in summary, the In-Memory feature is not disabled by default. It happens to be that the capacity-sizing parameter INMEMORY_SIZE is set to zero so the feature is unusable. However, setting both INMEMORY_QUERY and INMEMORY_SIZE does not constitute usage of the feature.

Confused? I’m not.

 

BLOG UPDATE 2014.07.29: Oracle’s Maria Colgan issued a tweet stating “What u found in you 3rd blog is a bug [...] Bug 19308780.” Click here for a screenshot of the tweet.

 

1 Response to “Oracle Database 12c In-Memory Feature – Part III. Enabled, Used or Confused? Don’t Be.”



  1. 1 Preventing standby databases opening in Active DataGuard mode + chopt !!! « Oracle DBA – A lifelong learning experience Trackback on August 6, 2014 at 10:40 am

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