12c

Jonathan Lewis's picture

In-memory DB

A recent thread on the OTN database forum supplied some code that seemed to show that In-memory DB made no difference to performance when compared with the traditional row-store mechanism and asked why not.  (It looked as if the answer was that almost all the time for the tests was spent returning the 3M row result set to the SQL*Plus client 15 rows at a time.)

The responses on the thread led to the question:  Why would the in-memory (column-store) database be faster than simply having the (row-store) data fully cached in the buffer cache ?

rshamsud's picture

RMOUG Training Days 2015

I will be talking in Rocky Mountain Oracle User Group Training Days 2015( http://www.rmoug.org), with live demos (hopefully there will be no failures in the demo). My topics are:

Feb 17: Deep dive: 3:15PM to 5:15PM – RAC 12c optimization: I will discuss RAC global cache layer in detail with a few demos. You probably can’t find these deep Global Cache layer details anywhere else </p />
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Jonathan Lewis's picture

Re-optimization

The spelling is with a Z rather than an S because it’s an Oracle thing.

Tim Hall has just published a set of notes on Adaptive Query Optimization, so I thought I’d throw in one extra little detail.

When the optimizer decides that a query execution plan involves some guesswork the run-time engine can monitor the execution of the query and collect some information that may allow the optimizer to produce a better execution plan. The interaction between all the re-optimization mechanisms can get very messy, so I’m not going to try to cover all the possibilities – read Tim’s notes for that – but one of the ways in which this type of information can be kept is now visible in a dynamic performance view.

oakroot's picture

[Oracle] Researching internal latch implementation (ksl_get_shared_latch, kslfre, kslgetsl_w) and crashing PMON

Introduction

Last week the DOAG 2014 conference took place in Nuremberg and it was a blast with a lot of useful presentations and especially great conversations and meet ups with Oracle friends. I had a nice talk about the Oracle latch implementation with a participant, who told me that his instance crashes every time, if he (manually) sets a shared latch in exclusive mode and tries to release it afterwards. It sounded really interesting as i have done this so many times without ever noticing such an issue. He also told me that this issue is reproducible at least on Oracle 11g R2 and 12c R1. I had no immediate answer or clue about the described issue and needed to research it furthermore.

Richard Foote's picture

12.1.0.2 Introduction to Zone Maps Part III (Little By Little)

I’ve previously discussed the new Zone Map database feature and how they work in a similar manner to Exadata Storage indexes. Just like Storage Indexes (and conventional indexes for that manner), they work best when the data is well clustered in relation to the Zone Map or index. By having the data in the table […]

Kerry Osborne's picture

ECO 2014 Slides

Just a quick note that I posted slides for the 2 talks I did at ECO in Raleigh this week:

Keynote: Creative Problem Solving (for Oracle Systems)

In-Memory In Action (slides by Tanel Poder) :)

Great crowd. I really enjoyed myself.

Note: You can also find other presentations on my Whitepapers/Presentations page via the link at the top of the screen.

Kerry Osborne's picture

Interesting Oracle Syntax Error

As shared by a well known Oracle and Big Data performance geek!

SQL> ALTER SYSTEM SET inmemory_size = 5T SCOPE=spfile;
ALTER SYSTEM SET inmemory_size = 5T SCOPE=spfile
*
ERROR at line 1:
ORA-32005: error while parsing size specification [5T]


SQL> ALTER SYSTEM SET inmemory_size = 5120G SCOPE=spfile;

System altered.

:)

Richard Foote's picture

Index Advanced Compression vs. Bitmap Indexes (Candidate)

A good question from Robert Thorneycroft I thought warranted its own post. He asked: “I have a question regarding bitmapped indexes verses index compression. In your previous blog titled ‘So What Is A Good Cardinality Estimate For A Bitmap Index Column ? (Song 2)’ you came to the conclusion that ‘500,000 distinct values in a 1 […]

Richard Foote's picture

12.1.0.2 Introduction to Zone Maps Part II (Changes)

In Part I, I discussed how Zone Maps are new index like structures, similar to Exadata Storage Indexes, that enables the “pruning” of disk blocks during accesses of the table by storing the min and max values of selected columns for each “zone” of a table. A Zone being a range of contiguous (8M) blocks. I […]

oakroot's picture

[Oracle] - New diagnostic event "wait_event[]" (and others) for troubleshooting / researching purpose with Oracle 12c

Introduction

A long time has gone since my last blog post on SCN in March 2014, but i was quite busy with Oracle RAC implementations and troubleshooting performance issues in the last month. It was a quite interesting time for me and i have learned a lot of new stuff about Oracle 12c and so in consequence this is just a tiny blog post about a new diagnostic event called "wait_event[]", which was introduced with Oracle 12c R1 (12.1.0.1). Oracle has re-engineered its kernel diagnostics & tracing infrastructure with Oracle 11g, which allows you to be much more detailed and extensive by tracing and dumping diagnostic / low level (internals) information. Please check the reference section for more detailed information about that "new" kernel diagnostics & tracing infrastructure, if you have never heard of it until yet.

 

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