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Kevin Closson

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Updated: 4 hours 49 min ago

SLOB Physical I/O Randomness. How Random Is Random? Random!

Sun, 2014-08-24 11:29

I recently read a blog post by Kyle Hailey regarding some lack of randomness he detected in the Orion I/O generator tool. Feel free to read Kyle’s post but in short he used dtrace to detect Orion was obliterating a very dense subset of the 96GB file Orion was accessing.

I’ve used Orion for many years and, in fact, wrote my first Orion related blog entry about 8 years ago. I find Orion to be useful for some things and of course DBAs must use Orion’s cousin CALIBRATE_IO as a part of their job. However, neither of these tools perform database I/O. If you want to see how database I/O behaves on a platform it’s best to use a database. So, SLOB it is. But wait! Is SLOB is just another storage cache-poking randomness-challenged distraction from your day job? No, it isn’t.

But SLOB Is So Very Difficult To Use

It’s quite simple actually. You can see how simple SLOB is to set up and test by visiting my picture tutorial.

How Random Is Random? Random!

SLOB is utterly random. However, there are some tips I’d like to offer in this post to show you how you can choose even higher levels of randomness in your I/O testing.

Kyle used dtrace and some shell commands to group block visits into buckets. Since I’m analyzing the randomness of SLOB I’ll use a 10046 trace on the database sessions. First I’ll run a 96 user SLOB test with slob.conf->UPDATE_PCT=0.

After the SLOB test was completed I scrambled around to find the trace files and worked out a simple set of sed(1) expressions to spit out the block numbers being visited by each I/O of type db file sequential read:

how-random2

I then grouped the blocks being visited into buckets much the same way Kyle did in his post:

how-random3

I’ll show some analysis of the those buckets later in the post.  Yes, SLOB is random as analysis of 96u.blocks.txt will show but it can be even more random if one configures a RECYCLE buffer pool. One of the lesser advertised features of SLOB is the fact that all working tables in the SLOB schemas are created with BUFFER_POOL RECYCLE in the storage clause. The idea behind this is to support the caching of index blocks in the SGA buffer pool. When no RECYCLE pool is allocated there is a battle for footprint in the SGA buffer pool causing even buffers with index blocks to be reused for buffering table/index blocks of the active transactions. Naturally when indexes are not cached there will be slight hot-spots for constant, physical, re-reads of the index blocks. The question becomes what percentage of the I/O do these hot blocks account for?

To determine how hot index blocks are I allocated a recycle buffer pool and ran another 2 minute SLOB test. As per the following screen shot I again grouped block visits into buckets:

how-random4

After having both SLOB results (with and without RECYCLE buffer pool) I performed a bit of text processing to determine how different the access patterns were in both scenarios. The following shows:

  • The vast majority of blocks are visited 10 or less times in both models
  • The RECYCLE pool model clearly flattens out the re-visit rates as the hotest block is visited only 12 times compared to the 112 visits for the hottest block in the default case
  • If 12 is the golden standard for sparsity (as per the RECYCLE pool test case) then even the default is quite sparse because dense buckets accounted for only 84,583 physical reads compared to the nearly 14 million reads of blocks in the sparse buckets

how-random5

The following table presents the data including the total I/O operations traced. The number of sparse visits are those blocks that were accessed less than or equal to 10 times during the SLOB test. I should point out that there will naturally be more I/O during a SLOB test when index accesses are forced physical as is the case with the default buffer pools. That is, the RECYCLE buffer pool case will have a slightly higher logical I/O rate (cache hits) due to index buffer accesses.

table

Summary

If you want to know how database I/O performs on a platform use a database. If using a database to test I/O on a platform then by all means drive it with SLOB ( a database I/O tool).

Regarding randomness, even in the default case SLOB proves itself to be very random. If you want to push for even more randomness then the way forward is to configure db_recycle_cache_size.

Enjoy SLOB! The best place to start with SLOB is the SLOB Resources Page.

 

 

 

 

 

 


Filed under: oracle, Oracle I/O Performance, Oracle11g, Oracle11g RAC, SLOB Tagged: Oracle Exadata Storage Server, Oracle I/O Performance, Oracle Performance, Random I/O, SLOB

Oracle Database 12c In-Memory Feature – Part V. You Can’t Use It If It’s Not “Enabled.” Not Being Able To Use A Feature Is An Important “Feature.”

Fri, 2014-08-15 13:04

This is part 5 in a series: Part I, Part II, Part III, Part IV, Part V.

Synopsis

This blog post is the last word on the matter.

Enabled?  It’s About Usage!

You don’t get charged for Oracle feature usage unless you use the feature. So why does Oracle inconsistently use the word enabled when we care about usage? If enabled precedes usage then enabled is a sanctified term. Please read on…

It’s All About Getting The Last Word? No, It’s About Taking Care Of Customers.

On August 6, 2014  Oracle shared their last word and official statement on the matter of bug-ridden tracking of the Oracle Database 12c  In-Memory feature usage in a quote to the press at CBR. I’ll paraphrase first and then quote the article. Here is what I hear when I read the words of Oracle’s spokesman:

Yeah, my bad, we have a bug. The defective code erroneously tracks feature usage for an Enterprise Edition additional cost option priced at $23,000 per processor core. Don’t worry. When we track this particular feature usage we’ll ignore it should you be audited. You have our spoken word that we’ll just shine this one on. Here, let me trade a few confusing words about usage without using the word enabled or disabled since those are taboo.

My paraphrase probably draws a more serene picture than the visions of tip-toeing and side-stepping conjured up by the following words I’ll quote from the CBR article. Bear in mind the fact that the bug spoken of in the quote is 19308780–a bug, by the way, that is not readable by maintenance contract holders. Now I’ll quote the article:

Recording that the In-Memory option is in use in this case is a bug and we will fix it in the first patchset update coming in October.

Yes, we knew it was a bug. I merely had to do the hard work of getting Oracle to acknowledge it. The article continued with the following quote. Please ignore the fact that Oracle’s spokesman refers to me common. Focus instead on the fact that throughout parts 1 through 4 in my series I suffered erroneous  feature usage reporting because of a bug (software defect). I quote:

Kevin initially claimed that feature tracking could report In-Memory usage, and therefore impact licensing, without the end-user doing anything. This was and is still not the case. Customer licensing of Oracle Database In-Memory is not impacted by the bug that Maria notes in her blog. When an end-user explicitly undertakes actions to set the INMEMORY attribute on a table but the In-Memory column store has not been allocated (by setting the inmemory_size parameter to a non zero value), the bug results in feature tracking incorrectly reporting In-Memory ‘in use’. However as no column store has been allocated, the feature is not in use and therefore there is no licensing impact.

 

Ah yes. The old, “it’s not in use but it reports it’s in use situation.” That’s could have been conveyed in very short sentences…could have.

Since the bug spoken of in the above quote is not visible to contract holders I’m just going to let you mull over the circular logic.  This whole situation could be a lot simpler if Oracle would either a) make a bug description visible to contract holders so customers know what is broken and how to test whether it got fixed when the patch is eventually applied and/or b) add this defect to MOS 1309070.1 which is a bug that tracks all the other bugs in feature usage reporting. Yes, indeed, there are other bugs of this sort with other features. All software has bugs.

Last Word On The Matter

My last word on the matter has to do with the fact that the feature cannot be unlinked. It is a very expensive–and very useful, important feature. As I pointed out in Part II the feature cannot be absolutely disabled at the executable level as is the case for other high cost options like Real Application Clusters and Partitioning.  I think Oracle is trying to tell us it is impossible computer science to make it an unlinkable feature–at least that’s how I interpret the following words in a blog post at Oracle.com:

Oracle Database In-Memory is not a bolt on technology to the Oracle Database. It has been seamlessly integrated into the core of the database as a new component of the Shared Global Area (SGA). When the Oracle Database is installed, Oracle Database In-Memory is installed. They are one and the same. You can’t unlink it or choose not to install it.

Now maybe this is not saying there is no way to code the feature as unlinkable. Maybe it’s saying the choice was made to not make it unlinkable. I don’t know. If, however, we are to believe that the mere fact the feature uses the SGA makes  it some sort of atomic-level symbiotic parasite, well, that argument doesn’t  hold water. Indeed, Real Application Clusters is massively integrated with the SGA. Ever heard of Cache Fusion? With Cache Fusion data blocks get shuttled from one SGA to another across hosts in a cluster! Real Application Clusters is unlinkable–that’s unthinkable!

 

What Is Unlinkable Anyway

There might be folks that don’t know what we mean when we say a feature is unlinkable. This doesn’t mean all the code for the feature is yanked out of the binary. It simply means that a single–or perhaps a few–binary objects are linked into the Oracle executable that enables the feature. If unlinked there is absolutely no way to use the feature–as is the case with, for instance, Real Application Clusters.

And not being able to use the feature is an important feature!

So let’s ponder the insurmountable computer science that must surely be involved in implementing the In-Memory Column Store feature as unlinkable.

Oracle has told us the INMEMORY_SIZE initialization parameter is the on/off  button for the feature. That means there is a single, central on/off button that is, indeed, able to be manipulated even by the user. Can you imagine how difficult it must be to implement a global variable–even a simple boolean–that get’s linked in and checked when one boots the database? Not hard to grasp. What if the variable had a silly name like inmemory_deactivated. What if the feature activation module–let’s call it inmem.o–had inmemory_deactived=TRUE but an alternate module called  inmemON.o had inmemory_deactivated=FALSE. In much the same way we relink Real Application Clusters, the link scripts manipulate the file name so that the default (with feature deactivated) gets replaced with the activated module–only if the user wants the possibility of using the feature. How would all this deep, dark, complex code come together? Well, when the database instance is booted inmemory_deactivated is evaluated and regardless of the user’s setting of INMEMORY_SIZE the In-Memory feature is really, truly, disabled–and most importantly not usable. No possibility for confusion. Would that be better than a game of Licensed-Feature Usage Prevention Twister(tm)?

1966_Twister_Cover

Intensely Deep Engineering Difficulty

Now, imagine that. We didn’t even have to use the back of a cocktail napkin to draw out a solution to the mysteries behind how utterly unlinkable the In-Memory Database feature must surely be. We simply a)  drew upon our understanding of other SGA-integrated features like Real Application Clusters and b) recalled how unlinking works for other features and c) drew upon our basic level understanding of the C programming language vis a vis global variables and object linking.

Let me summarize all that: There is a single user-modifiable boot-time parameter that disables In-Memory Database as per Oracle’s blog and spokesman assertions. Um, that’s a pretty simple focal point to make the feature unlinkable.

Summary

Yes, Oracle could implement a method for making the In-Memory Column Store feature an unlinkable option just like they did for Real Application Clusters. I can only imagine why they chose not to (visions of USD $23,000 per processor core).


Filed under: oracle

SLOB Data Loading Case Studies – Part I. A Simple Concurrent + Parallel Example.

Wed, 2014-08-06 02:21
Introduction

This is Part I in a short series of posts dedicated to loading SLOB data.  The SLOB loader is called setup.sh and it is, by default a concurrent, data loader. The SLOB configuration file parameter controlling the number of concurrent data loading threads is called LOAD_PARALLEL_DEGREE. In retrospect I should have named the parameter LOAD_CONCURRENT_DEGREE because unless Oracle Parallel Query is enabled there is no parallelism in the data loading procedure. But if LOAD_PARALLEL_DEGREE is assigned a value greater than 1 there is concurrent data loading.

Occasionally I hear of users having trouble with combining Oracle Parallel Query with the concurrent SLOB loader. It is pretty easy to overburden a system when doing something like concurrent, parallel data loading–in the absence of tools like Database Resource Management I suppose. To that end,  this series will show some examples of what to expect when performing SLOB data loading with various init.ora settings and combinations of parallel and concurrent data loading.

In this first example I’ll show an example of loading with LOAD_PARALLEL_DEGREE set to 8. The scale is 524288 SLOB rows which maps to 524,288 data blocks because SLOB forces a single row per block. Please note, the only slob.conf parameters that affect data loading are LOAD_PARALLEL_DEGREE and SCALE. The following is a screen shot of the slob.conf file for this example:

SLOB-data-load-3

The next screen shot shows the very simple init.ora settings I used during the data loading test. This very basic initialization file results in default Oracle Parallel Query, therefore  this example is a concurrent + parallel data load.

SLOB-data-load-6

The next screen shot shows that I directed setup.sh to load 64 SLOB schemas into a tablespace called IOPS. Since SCALE is 524,288 this example loaded roughly 256GB (8192 * 524288 * 64) of data into the IOPS tablespace.

SLOB-data-load-1

As reported by setup.sh the data loading completed in 1,539 seconds or a load rate of roughly 600GB/h. This loading rate by no means shows any intrinsic limit in the loader. In future posts in this series I’ll cover some tuning tips to improve data loading.  The following screen shot shows the storage I/O rates in kilobytes during a portion of the load procedure. Please note, this is a 2s16c32t 115w Sandy Bridge Xeon based server. Any storage capable of I/O bursts of roughly 1.7GB/s (i.e., 2 active 8GFC Fibre Channel paths to any enterprise class array) can demonstrate this sort of SLOB data loading throughput.

SLOB-data-load-2

 

After setup.sh completes it is good to count how many loader threads were able to successfully load the specified number of rows. As the example shows I simply grep for the value of slob.conf->SCALE from cr_tab_and_load.out. Remember, SLOB in its current form, loads a zeroth schema so the return from such a word count (-l) should be one greater than the number of schemas setup.sh was directed to load.

SLOB-data-load-4

The next screen shot shows the required execution of the procedure.sql script. This procedure must be executed after any execution of setup.sh.

SLOB-data-load-7

Finally, one can use the SLOB/misc/tsf.sql script to report the size of the tablespace used by setup.sh. As the following screenshot shows the  IOPS tablespace ended up with a  little over 270GB which can be accounted for by the size of the tables based on slob.conf, the number of schemas and a little overhead for indexes.

 

SLOB-data-load-5

Summary

This installment in the series has shown expected screen output from a simple example of data loading. This example used default Oracle Parallel Query settings, a very simple init.ora and a concurrent loading degree of 8 (slob.conf->LOAD_PARALLEL_DEGREE) to load data at a rate of roughly 600GB/h.

 

 

 


Filed under: oracle

SLOB Deployment – A Picture Tutorial.

Mon, 2014-08-04 19:31

SLOB can be obtained at this link: Click here.

This post is just a simple set of screenshots I recently took during a fresh SLOB deployment. There have been a tremendous number of SLOB downloads lately so I thought this might be a helpful addition to go along with the documentation. The examples I show herein are based on a 12.1.0.2 Oracle Database but these principles apply equally to 12.1.0.1 and all Oracle Database 11g releases as well.

Synopsis
  1. Create a tablespace for SLOB.
  2. Run setup.sh
  3. Verify user schemas
  4. Create The SLOB procedure In The USER1 Schema
  5. Execute runit.sh. An Example Of Wait Kit Failure and Remedy
  6. Execute runit.sh Successfully
  7. Using SLOB With SQL*Net
    1. Test SQL*Net Configuration
    2. Execute runit.sh With SQL*Net
  8. More About Testing Non-Linux Platforms

 

Create a Tablespace for SLOB

If you already have a tablespace to load SLOB schemas into please see the next step in the sequence.

SLOB-deploy-1

Run setup.sh

Provided database connectivity works with ‘/ as sysdba’ this step is quite simple. All you have to do is tell setup.sh which tablespace to use and how many SLOB users (schemas) load. The slob.conf file tells setup.sh how much data to load. This example is 16 SLOB schemas each with 10,000 8K blocks of data. One thing to be careful of is the slob.conf->LOAD_PARALLEL_DEGREE parameter. The name is not exactly perfect since this actually controls concurrent degree of SLOB schema creation/loading. Underneath the concurrency may be parallelism (Oracle Parallel Query) so consider setting this to a rather low value so as to not flood the system until you’ve practiced with setup.sh for a while.

 

SLOB-deploy-2

Verify Users’ Schemas

After taking a quick look at cr_tab_and_load.out, as per setup.sh instruction, feel free to count the number of schemas. Remember, there is a “zero” user so setup.sh with 16 will have 17 SLOB schema users.

SLOB-deploy-3

Create The SLOB Procedure In The USER1 Schema

After setup.sh and counting user schemas please create the SLOB procedure in the USER1 schema.

SLOB-deploy-4

Execute runit.sh. An Example Of Wait Kit Failure and Remedy

This is an example of what happens if one misses the detail to create the semaphore wait kit as per the documentation. Not to worry, simply do what the output of runit.sh directs you to do.

SLOB-deploy-5

Execute runit.sh Successfully

The following is an example of a healthy runit.sh test.

SLOB-deploy-6

Using SLOB with SQL Net

Strictly speaking this is all optional if all you intend to do is test SLOB on your current host. However, if SLOB has been configured in a Windows, AIX, or Solaris box this is how one tests SLOB. Testing these non-Linux platforms merely requires a small Linux box (e.g., a laptop or a VM running on the system you intend to test!) and SQL*Net.

Test SQL*Net Configuration

We don’t care where the SLOB database service is. If you can reach it successfully with tnsping you are mostly there.

SLOB-deploy-7

Execute runit.sh With SQL*Net

The following is an example of a successful runit.sh test over SQL*Net.

SLOB-deploy-8

More About Testing Non-Linux Platforms

Please note, loading SLOB over SQL*Net has the same configuration requirements as what I’ve shown for data loading (i.e., running setup.sh). Consider the following screenshot which shows an example of loading SLOB via SQL*Net.

SLOB-deploy-9

Finally, please see the next screenshot which shows the slob.conf file the corresponds to the proof of loading SLOB via SQL*Net.

SLOB-deploy-10

 

Summary

This short post shows the simple steps needed to deploy SLOB in both the simple Linux host-only scenario as well as via SQL*Net. Once a SLOB user gains the skills needed to load and use SLOB via SQL*Net there are no barriers to testing SLOB databases running on any platform to include Windows, AIX and Solaris.

 

 

 

 

 


Filed under: oracle

Impugn My Character Over Technical Points–But You Should Probably Be Correct When You Do So. Oracle 12c In-Memory Feature Snare? You Be The Judge ‘Cause Here’s The Proof.

Mon, 2014-07-28 18:04

Press Coverage at The Register: Click here.

Executive Summary

This blog post offers proof that you can trigger In-Memory Column Store feature usage with the default INMEMORY_* parameter settings. These parameters are documented as the approach to ensure In-Memory functionality is not used inadvertently–or at least they are documented as the “enabling” parameters.

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?

 

Index of Related Posts

This is part 4 in a series: Part I, Part II, Part III, Part IV.

Other Blog Updates

Please note, blog updates are listed at the end of the article.

What Really Matters?

This is a post about enabling versus using the Oracle Database 12c Release 12.1.0.2 In-Memory Column Store feature which is a part of the separately licensed Database In-Memory Option of 12c. While reading this please be mindful that in this situation all that really matters is what actions on your part effect the internal tables that track feature usage.

Make Software, Not Enemies–And Certainly Not War

There is a huge kerfuffle regarding the separately licensed In-Memory Column Store feature in Oracle Database 12c Release 12.1.0.2–specifically how the feature is enabled and what triggers  usage of the feature.

I pointed out a) the fact that the feature is enabled by default and b) the feature is easily accidentally used. I did that in Part I and Part II in my series on the matter.  In Part III I shared how the issue has lead to industry journalists quoting–and then removing–said quotes. I’ve endured an ungodly amount of shameful backlash even from some friends on the Oaktable Network list as they asserted I was making a mole hill out of something that was a total lark (that was a euphemistic way of saying they all but accused me of misleading my readers).  I even had friends suggesting this is a friendship-ending issue. Emotion and high-technology are watery-oil like in nature.

About the only thing that hasn’t happened is for anyone to apologize for being totally wrong in their blind-faith rooted feelings about this issue. What did he say? Please read on.

From the start I pointed out that the INMEMORY_QUERY feature is enabled by default–and that it is conceivable that someone could use it accidentally. The back lash from that was along the lines of how many parameters and what user actions are needed for that to be a reality.  Maria Colgan–who is Oracle’ s PM for the In-Memory Column Store feature–tweeted that I’m confusing people when announcing her blog post on the fact that In-Memory Column Store usage is controlled not by INMEMORY_QUERY but instead INMEMORY_SIZE. Allow me to add special emphasis to this point. In a blog post on oracle.com, Oracle’s PM for this Oracle database  feature explicitly states that INMEMORY_SIZE must be changed from the default to use the feature.

If I were to show you everyone else was wrong and I was right, would you think less of me? Please, don’t let it make you feel less of them. We’re just people trying to wade through the confusion.

The Truth On The Matter

Here is the truth and I’ll prove it in a screen shot to follow:

  1. INMEMORY_QUERY is enabled by default. If it is set you can trigger feature usage–full stop.
  2. INMEMORY_SIZE is zero by default.  Remember this is the supposedly ueber-powerful setting that precludes usage of the feature and not, in fact, the top-level-sounding INMEMORY_QUERY parameter. As such this should be the parameter that would prevent you for paying for usage of the feature.

In the following screenshot I’ll show that INMEMORY_QUERY is at the default setting of ENABLE  and INMEMORY_SIZE is at the default setting of zero. I prove first there is no prior feature usage. I then issue a CREATE TABLE statement specifying INMEMORY.  Remember, the feature-blocking INMEMORY_SIZE parameter is zero.  If  “they” are right I shouldn’t be able to trigger In-Memory Column Store feature usage, right? Observe–or better yet, try this in your own lab:

proof-mu

So ENABLED Means ENABLED? Really? Imagine That.

So I proved my point which is any instance with the default initialization parameters can trigger feature usage. I also proved that the words in the following three screenshots are factually incorrect:

MariaCallingMeOut

Screenshot of blog post on Oracle.com:

maria-on-inmemory_size_assertion

Screenshot of email to Oracle-L Email list:

 

kerry

 

Summary

I didn’t want to make a mountain out of this mole hill. It’s just a bug. I don’t expect apologies. That would be too human–almost as human as being completely wrong while wrongly clinging to one’s wrongness because others are equally, well, wrong on the matter.

 

BLOG UPDATE 2014.07.31: Click here to view an article on The Register regarding Oracle Database In-Memory feature usage.

BLOG UPDATE 2014.07.30: Oracle’s Maria Colgan has a comment thread on her blog on the In-Memory Column Store feature. In the thread a reader reports precisely the same bug behavior you will see in my proof below. Maria’s comment is that feature usage is tracked in spite of the supposed disabling feature INMEMORY_SIZE set to the default value. While this agrees with what I  already knew about this feature it is in my opinion not sufficient to speak of a bug of such consequence without citing the bug number. Furthermore, such a bug must be visible to users with support contracts. Click here for a  screenshot of the Oracle blog. In case Oracle changes their mind on such an apparently sensitive topic I uploaded the blog to the Wayback Machine here

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. Also, click here for a Wayback Machine (web.archive.org) copy of the tweet.

 

 

Sundry References

 Print out of Maria’s post on Oracle.com and link to same: Getting started with Oracle Database In-Memory Part I

Franck Pachot 2014.07.23 findings reported here:  Tweet , screenshot of tweet.

 

 

 


Filed under: oracle

Oracle Database 12c Release 12.1.0.2 – My First Observations. Licensed Features Usage Concerns – Part II.

Fri, 2014-07-25 15:02
Preface

In this post you’ll see that I provide an scenario of accidental paid-feature “use.”  The key elements of the scenario are: 1) I enabled the feature (by “accident”) but 2) I didn’t actually use the feature because I neither created nor altered any tables.

In Part I of this series I aimed to bring to people’s attention what I see as a significant variation from the norm when it comes to Oracle licensed-option usage triggers and how to prevent them from being triggered. Oracle Database Enterprise Edition supports several separately licensed options such as Real Application Clusters, Partitioning, and so on.  A feature like Real Application Clusters is very expensive but if  “accidental usage” of this feature is a worry on an administrator’s mind there is a simple remedy: unlink it. If the bits aren’t in the executable you’re safe. Is that a convoluted procedure? No. An administrator simply executes make -d ins_rdbms.mk rac_off and then relinks the Oracle executable. Done.

What about other separately licensed options like Partitioning?  As I learned from Paul Bullen, once can use the Oracle-supplied chopt command to remove any chance of using Partitioning if, in fact, one does not want to use Partitioning. I thought chopt might be the solution to the issue of possible, accidental usage of the In-Memory Column Store feature/option. However, I found that chopt, as of this point, does not offer the ability to neutralize the feature as per the following screenshot.

img5

Trivial Pursuit of the Ignoramus or Mountainous Mole Hill?

There is yet no way I know of to prevent accidental use of the In-Memory Column Store feature/option. Am I just making a mountain out of a mole hill? I’ll let you be the judge. And if you side with folks that do feel this is a mountainous-mole hill you’d be in really good company.

Lest folks think that we Oaktable Network Members are a blind, mutual admiration society, allow me to share the rather sizzling feedback I got for raising awareness to this aspect of Oracle Database 12c:

oaktable-email-calls-bs

Geez!

No, I didn’t just want to dismiss this feedback. Instead  I pushed the belt-sander off of my face and read the words a couple of times. The author of this email asserted I’m conveying misinformation ( aka “BS”) and to fortify that position it was pointed out that one must:

  1. Set a database (instance initialization) parameter.
  2. Bounce the instance.
  3. Alter any object to use the feature. I’ll interpret that as a DDL action (e.g., ALTER TABLE, CREATE TABLE).

Even before I read this email I knew these assertions were false. We all make mistakes–this I know!  I should point out that unlike every release of Oracle from 5.1.17 to 11gR2 I was not invited to participate in the Beta for this feature. I think a lot of Oaktable Network members were in the program–perhaps even the author of the above email snippet–but I don’t know that for certain. Had I encountered this during a Beta test I would have raised it to the Beta manager as an issue and maybe, just maybe, the feature behavior might have changed before first customer ship. Why am I blabbering on about the Beta program? Well, given the fact that even Oaktable Network members with pre-release experience with this feature evidently do not know what I’m about to show in the remainder of this post.

What Is An Accident?

Better yet, what is an accident and how full of “BS” must one be to fall prey? Maybe the remainder of the post will answer that rhetorical question. Whether or not  it does, in fact, answer the question I’ll be done with this blog series and move on to the exciting work of performance characterization of this new, incredibly important feature.

Anatomy of a “Stupid Accident.”

Consider a scenario. Let’s say a DBA likes to use the CREATE DATABASE statement to create a database. Imagine that!  Let’s pretend for a moment that DBAs can be very busy and operate in chaotic conditions. In the fog of this chaos, a DBA could, conceivably, pull the wrong database instance initialization file (e.g., init.ora or SPFILE) and use it when creating a database. Let’s pretend for a moment I was that busy, overworked DBA and I’ll show you in the following happeneds:

  1. I executed sqlplus from the bash command prompt.
  2. I directed sqlplus to execute a SQL script called cr_db.sql. Many will recognize this as the simple little create script I supply with SLOB.
  3. The cr_db.sql script uses a local initialization parameter file called create.ora
  4. sqlplus finished creating the database. NOTE: this procedure does not create a single user table.
  5. After the database was created I connected to the instance and forced the feature usage tracking views to be updated (thanks to Morgan’s Library for that know-how as well…remember, I’m a database platform engineer not a DBA so I learn all the time in that space).
  6. I executed a SQL script to report feature usage of only those features that match a predicate such as “In-%’

 

img1

This screen shot shows that the list of three asserted must-happen steps (provided me by a fellow Oaktable Network member) were not, in fact, the required recipe of doom.  The output of the features.sql script proves that I didn’t even need to create a user table to trigger the feature.

The following screen shot shows what the cr_db.sql script does:

img2

The following screenshot shows the scripts I used to update the feature usage tracking views and to report against same:

img4

The “Solution” To The “Puzzle”

Stepping on a landmine doesn’t just happen. You have to sort of be on your feet and walking around for that to happen. In the same vein, triggering usage of the separately licensed Oracle Database 12c Release 12.1.0.2 In-Memory Column Store feature/option required me to be “on my feet and walking around” the landmine–as it were. Did I have to jump through hoops and be a raging, bumbling idiot to accidentally trigger usage of this feature? No. Or, indeed, did I issue a single CREATE TABLE or ALTER TABLE DDL statement? No. What was my transgression? I simply grabbed the wrong database initialization parameter file from my repository–in the age old I’m-only-human sort of way these things often happen.

To err to such a degree would certainly not be human, would it?

The following screenshot shows the parameter file I used to prove:

  1. You do not need to alter parameters and bounce an instance to trigger this feature usage in spite of BS-asserting feedback from experts.
  2. You don’t even have to create a single application table to trigger this feature usage.

img3

Summary

This blog thread has made me a feel a little like David Litchfield must have surely felt for challenging the Oracle9i-era claims of how Oracle Database was impenetrable by database security breaches. We all know how erroneous those claims where. Unbreakable, can’t break it, can’t break in?

Folks, I know we all have our different reasons to be fans of Oracle technology–and, indeed, I am a fan. However, I’m not convinced that unconditional love of a supposed omnipotent and omniscient god-like idol are all that healthy for the IT ecosystem. So, for that reason alone I have presented these findings. I hope it makes at least a couple of DBAs aware of how this licensed feature differs from other high-dollar features like Real Application Clusters in exactly what it takes to “use” the feature–and, moreover, how to prevent stepping on a landmine as it were.

 

…and now, I’m done with this series.

 

 


Filed under: oracle

Oracle Database 12c Release 12.1.0.2 – My First Observations. Licensed Features Usage Concerns – Part I.

Thu, 2014-07-24 02:12

My very first words on Oracle Database 12c Release 12.1.0.2 can be summed up in a single quotable quote:

This release is hugely important.

I’ve received a lot of email from folks asking me to comment on the freshly released In-Memory Database Option. These words are so overused. This post, however, is about much more than word games. Please read on…

When querying the dba_feature_usage_statistics view the option is known as “In-Memory Column Store.”  On the other hand, I’ve read a paper on oracle.com that refers to it as the “In-Memory Option” as per this screen shot:

in-memory-paper

A Little In-Memory Here, A Little In-Memory There

None of us can forget the era when Oracle referred to the flash storage in Exadata as a “Database In-Memory” platform. I wrote about all that in a post you can view here: click this. But I’m not blogging about any of that. Nonetheless, I remained confused about the option/feature this morning as I was waiting for my download of Oracle Database 12c Release 12.1.0.2 to complete. So, I spent a little time trying to cut through the fog and get some more information about the In-Memory Option. My first play was to search for the term in the search bar at oracle.com. The following screen shot shows the detritus oracle.com returned due to the historical misuse and term overload–but, please, remember that I’m not blogging about any of that:

In-Memory-12c-Oraclecom-Pollution

As the screenshot shows one must eyeball their way down through 8 higher-ranking search results that have nothing to do with this very important new feature before one gets to a couple of obscure blog links. All this term overload and search failure monkey-business is annoying, yes, but I’m not blogging about any of that.

What Am I Blogging About?

This is part I in a short series about Oracle licensing ramifications of the In-Memory Option/In-Memory Column Store Feature.

The very first thing I did after installing the software was to invoke the SLOB database create scripts to quickly get me on my way. The following screen shot shows how I discovered that the separately-licensed In-Memory Option/In-Memory Column Store Feature is enabled by default:

inmem1

Now, this is no huge red flag because separately-licensed features like Real Application Clusters and Partitioning are sort of “on” by default. This doesn’t bother me because a) one can simply unlink RAC to be safe from accidental usage and b) everyone that uses Enterprise Edition uses the Partitioning Option (I am correct on that assertion, right?).  However, I think things are a little different with the In-Memory Option/In-Memory Column Store Feature since it is “on” by default and a simple command like the one in the following screen shot means your next license audit will be, um, more entertaining.

in-mem-timebomb

OK, please let me point out  that I’m trying as hard as I can to not make a mountain out of a mole-hill. I started this post by stating my true feelings about this release. This release is, indeed, hugely important. That said, I do not believe for a second that every Enterprise Edition deployment of Oracle Database 12c Release 12.1.0.2 will need to have the In-Memory Option/In-Memory Column Store Feature in the shopping cart–much unlike Partitioning for example. Given the crushing cost of this option/feature I expect that its use will be very selective. It’s for this reason I wanted to draw to people’s attention the fact that–in my assessment–this option/feature is very easy to use “accidentally.” It really should have a default initialization setting that renders the option/feature nascent–but the reality is quite the opposite.

Summary

I have to make this post short and relegate it to part I in a series because I can’t take it to the next level which is to write about monitoring the feature usage. Why? Well, as I tweeted earlier today, the scripts most widely used for monitoring feature usage are out of date because they don’t (yet) report on the In-Memory Column Store feature. The scripts I allude to are widely known by Google search as MOS 1317265.1. Once these are updated to report usage of the In-Memory Option/In-Memory Column Store Feature I’ll post part II in the series.

Thoughts?

 

 

 


Filed under: oracle

When Storage is REALLY Fast Even Zero-Second Wait Events are Top 5. Disk File Operations I/O: The Mystery Wait Event.

Fri, 2014-07-18 09:37

The SLOB code that is generally available here differs significantly from what I often test with in labs. Recently I was contorting SLOB to hammer an EMC XtremIO All-Flash Array in a rather interesting way. Those of you in the ranks of the hundreds of SLOB experts out there will notice two things quickly in the following AWR snippet:

1)   Physical single block reads are being timed by the Oracle wait interface at 601 microseconds (3604/5995141 == .000601) and this is, naturally for SLOB, the top wait event.

2)   Disk file operations I/O is ranking as a top 5 timed event. This is not typical for SLOB.

 

file-io-operations

The 601us latencies for XtremIO are certainly no surprise. After all, this particular EMC storage array is an All-Flash Array so there’s no opportunity for latency to suffer as is the case with alternatives such as flash-cache approaches. So what is this blog post about? It’s about Disk file operations I/O.

I needed to refresh my memory on what the Disk file operations I/O event was all about. So, I naturally went to consult the Statistics Description documentation. Unfortunately there was no mention of the wait even there so I dug further to find it documented in the Description of Wait Events section of the Oracle Database 11g documentation which states:

This event is used to wait for disk file operations (for example, open, close, seek, and resize). It is also used for miscellaneous I/O operations such as block dumps and password file accesses.

Egad. A wait is a blocking system call. Since open(2)/close(2) and seek(2) are non-blocking on normal files I suppose I could have suffered a resize operation–but wait, this tablespace doesn’t allow autoextend.  I suppose I really shouldn’t care that much given the fact that the sum total of wait time was zero seconds. But I wanted to understand more so I sought information from the user community–a search that landed me happily at Kyle Hailey’s post on oaktableworld.com here. Kyle’s post had some scripts that looked promising for providing more information about these waits but unfortunately in my case the scripts returned no rows found.

So, at this point, I’ll have to say that the sole value of this blog post is to point out the fact that a) the Oracle documentation specifically covering statistics descriptions is not as complete as the Description of Wait Events section and b) the elusive Disk file operations I/O wait event remains, well, elusive and that this is now part I in a multi-part blog series until I learn more. I’ll set up some traces and see what’s going on. Perhaps Kyle will chime in.

 

 

 


Filed under: oracle

Interesting SLOB Use Cases – Part I. Studying ZFS Fragmentation. Introducing Bart Sjerps.

Thu, 2014-07-17 10:35

This is the first installment in a series of posts I’m launching to share interesting use cases for SLOB. I have several installments teed up but to put a spin on things I’m going to hit two birds with one stone in this installment. The first bird I’ll hit is to introduce a friend and colleague, Bart Sjerps, who I just added to my blogroll. The other bird in my cross-hairs is this interesting post Bart wrote some time back that covers a study of ZFS fragmentation using SLOB.

Bart Sjerps on ZFS Fragmentation. A SLOB study.

As always, please visit the SLOB Resources Page for SLOB kit and documentation.

 


Filed under: Silly Little Oracle Benchmark, SLOB, ZFS, ZFS Performance

EMC XtremIO – The Full-Featured All-Flash Array. Interested In Oracle Performance? See The Whitepaper.

Fri, 2014-07-11 16:32

NOTE: There’s a link to the full article at the end of this post.

I recently submitted a manuscript to the EMC XtremIO Business Unit covering some compelling lab results from testing I concluded earlier this year. I hope you’ll find the paper interesting.

There is a link to the full paper at the bottom of this block post. I’ve pasted the executive summary here:

Executive Summary

Physical I/O patterns generated by Oracle Database workloads are well understood. The predictable nature of these I/O characteristics have historically enabled platform vendors to implement widely varying I/O acceleration technologies including prefetching, coalescing transfers, tiering, caching and even I/O elimination. However, the key presumption central to all of these acceleration technologies is that there is an identifiable active data set. While it is true that Oracle Database workloads generally settle on an active data set, the active data set for a workload is seldom static—it tends to move based on easily understood factors such as data aging or business workflow (e.g., “month-end processing”) and even the data source itself. Identifying the current active data set and keeping up with movement of the active data set is complex and time consuming due to variability in workloads, workload types, and number of workloads. Storage administrators constantly chase the performance hotspots caused by the active dataset.

All-Flash Arrays (AFAs) can completely eliminate the need to identify the active dataset because of the ability of flash to service any part of a larger data set equally. But not all AFAs are created equal.

Even though numerous AFAs have come to market, obtaining the best performance required by databases is challenging. The challenge isn’t just limited to performance. Modern storage arrays offer a wide variety of features such as deduplication, snapshots, clones, thin provisioning, and replication. These features are built on top of the underlying disk management engine, and are based on the same rules and limitations favoring sequential I/O. Simply substituting flash for hard drives won’t break these features, but neither will it enhance them.

EMC has developed a new class of enterprise data storage system, XtremIO flash array, which is based entirely on flash media. XtremIO’s approach was not simply to substitute flash in an existing storage controller design or software stack, but rather to engineer an entirely new array from the ground-up to unlock flash’s full performance potential and deliver array-based capabilities that are unprecidented in the context of current storage systems.

This paper will help the reader understand Oracle Database performance bottlenecks and how XtremIO AFAs can help address such bottlenecks with its unique capability to deal with constant variance in the IO profile and load levels. We demonstrate that it takes a highly flash-optimized architecture to ensure the best Oracle Database user experience. Please read more:  Link to full paper from emc.com.


Filed under: All Flash Array, Flash Storage for Databases, oracle, Oracle I/O Performance, Oracle performance, Oracle Performnce Monitoring, Oracle SAN Topics, Oracle Storage Related Problems