Oracle database internals by Riyaj

Discussions about Oracle performance tuning, RAC, Oracle internal & E-business suite.

Archive for the ‘Presentations’ Category

All about RAC and MTU with a video

Posted by Riyaj Shamsudeen on May 22, 2012

Let’s first discuss how RAC traffic works before continuing. Environment for the discussion is: 2 node cluster with 8K database block size, UDP protocol is used for cache fusion. (BTW, UDP and RDS protocols are supported in UNIX platform; whereas Windows uses TCP protocol).

UDP protocol, fragmentation, and assembly

UDP Protocol is an higher level protocol stack, and it is implemented over IP Protocol ( UDP/IP). Cache Fusion uses UDP protocol to send packets over the wire (Exadata uses RDS protocol though).

MTU defines the Maximum Transfer Unit of an IP packet. Let us consider an example of MTU set to 1500 in a network interface. One 8K block transfer can not be performed with just one IP packet  as the IP packet size (1500 bytes) is less than 8K. So, one transfer of UDP packet of 8K size is fragmented to 6 IP packets and sent over the wire. In the receiving side, those 6 packets are reassembled to create one UDP buffer of size 8K. After the assembly, that UDP buffer is delivered to an UDP port of a UNIX process. Usually, a foreground process will listen on that port to receive the UDP buffer.

Read the rest of this entry »

Posted in 11g, Oracle database internals, Performance tuning, Presentations, RAC, video | Tagged: , , , , , , , , , , , , , , , , , , | 11 Comments »


Posted by Riyaj Shamsudeen on April 19, 2012

If you are attending Collaborate 2012, you might be interested in my content-rich sessions below :

Session Number: 326
Session Title: SCAN, VIP, HAIP, and other RAC acronyms
Session Date/Time/Room: Tue, Apr 24, 2012 (10:45 AM – 11:45 AM) : Surf C

Session Number: 327
Session Title: Internals and Performance Boot Camp: Truss, pstack, pmap, and more
Session Date/Time/Room: Wed, Apr 25, 2012 (03:00 PM – 04:00 PM) : Palm A

Hope to see you there!

Update: I am uploading presentation files. Presentations are much more recent than the document :-)


Thanks for attending!

Posted in Oracle database internals, Performance tuning, Presentations, RAC | Tagged: , , , , , , , , , , , , | 1 Comment »

Next Advanced RAC Training class scheduled.

Posted by Riyaj Shamsudeen on February 27, 2012

Just a quick note, I will be conducting next 2-week advanced RAC Training, online class in March 26-30 and April 9-13.

You can find agenda and other details here .

Update 1:
I received few emails about the training outline. You can find the outline below:


Update 2:
Yes, I do accept Purchase Orders and can invoice you :)

Posted in Presentations, RAC | Tagged: , , | 1 Comment »


Posted by Riyaj Shamsudeen on February 10, 2012

I just uploaded my presentation materials for ‘Truss, pstack etc’ for HOTSOS 2012 symposium , a performance intensive conference, happening right here in my home town Dallas, TX.

I can’t believe, it is been ten years from the start of this annual conference! This is the tenth annual symposium and I have been presenting in this symposium for almost all years except few early years. Quality of presentations and quality of audience is very high in this symposium and many of the audience are repeat audience, almost this feels like an annual pilgrimage to “sanctum of performance”. If you are interested in learning the techniques and methods to debug and resolve performance issues in a correct way, you should definitely consider attending this symposium. To top it off, Jonathan Lewis is conducting Training Day this year.

There are many great authors talking in this symposium.

Let me take this opportunity to welcome you to Dallas and encourage you to attend this symposium !
PS: Mark Bobak has been presenting or attending all ten years of this symposium, kudos Mark! And, Yes, that’s the same Mark Bobak who is the list admin for that most famous oracle-l mailing list.
PPS: Even though I live in Texas, no, I do not ride an horse to commute, instead, I drive a Ford Mustang car.(Incidentally, Mustang means “a small breed of horse, often wild or half wild, found in the southwestern US” as defined by, So, after all, I am driving a string of wild horse).

Posted in Performance tuning, Presentations, RAC | Tagged: , , | 1 Comment »

My sessions in RMOUG 2012

Posted by Riyaj Shamsudeen on February 10, 2012

I will be leaving to Denver in few days to talk about the following presentations in RMOUG 2012. Stop by and say hello to me if you intend to attend RMOUG training days.

My sessions in RMOUG 2012 are

  1. Room 402:Session 2: Parallel Execution in RAC – Wednesday 10:45 AM to 11:45AM
  2. Room 4f: Session 10: Troubleshooting RAC background processes – Thursday 1:30PM to 2:30PM
  3. Room 4f: Session 11: A kind and Gentle introduction to RAC – Thursday 2:45 PM to 3:45 PM

Hope to see you there.

Posted in Performance tuning, Presentations, RAC | Tagged: , , , | 2 Comments »

Video: deep review of LMS

Posted by Riyaj Shamsudeen on January 20, 2012

This video was created circa July 2011. Click the Read More link to review the video. Version Oracle Database

Synopsis: Essentially, we probe the importance of LMS processes using DTrace. Explain why LMS should run in elevated priority. How to review deep statistics about LMS processes and much more.

Posted in Oracle database internals, Performance tuning, Presentations, RAC, video | Tagged: , , , , | 7 Comments »

gc cr disk read

Posted by Riyaj Shamsudeen on January 13, 2012

You might encounter RAC wait event ‘gc cr disk read’ in 11.2 while tuning your applications in RAC environment. Let’s probe this wait event to understand why a session would wait for this wait event.

Understanding the wait event

Let’s say that a foreground process running in node 1, is trying to access a block using a SELECT statement and that block is not in the local cache. To maintain the read consistency, foreground process will require the block consistent with the query SCN. Then the sequence of operation is(simplified):

  1. Foreground session calculates the master node of the block; Requests a LMS process running in the master node to access the block.
  2. Let’s assume that block is resident in the master node’s buffer cache. If the block is in a consistent state (meaning block version SCN is lower (or equal?) to query SCN), then LMS process can send the block to the foreground process immediately. Life is not that simple, so, let’s assume that requested block has an uncommitted transaction.
  3. Since the block has uncommitted changes, LMS process can not send the block immediately. LMS process must create a CR (Consistent Read) version of the block: clones the buffer, applies undo records to the cloned buffer rolling back the block to the SCN consistent with the requested query SCN.
  4. Then the CR block is sent to the foreground process.

LMS is a light weight process

Global cache operations must complete quickly, in the order of milli-seconds, to maintain the overall performance of RAC database. LMS is a critical process and does not do heavy lifting tasks such as disk I/O etc. If LMS process has to initiate I/O, instead of initiating I/O, LMS will downgrade the block mode and send the block to the requesting foreground process (this is known as Light Works rule). Foreground process will apply undo records to the block to construct CR version of the block.

Read more

Posted in 11g, Oracle database internals, Performance tuning, Presentations, RAC | Tagged: , | 6 Comments »

RMOUG 2012 – Hello Denver!

Posted by Riyaj Shamsudeen on January 10, 2012

On February 14-16, I’ll be at the Colorado Convention Center in Denver, Colorado for RMOUG’s Training Days Conference. This is the largest regional Oracle User Conference in North America and attracts presenters from all around the country and the globe. I’ll be presenting:

Presentation Name: Troubleshooting RAC Background Process

Abstract: RAC background process performance is critical to keep the application performance. This session will demo techniques to review the performance of RAC background processes such as LMS, LMD, LMON, etc. using various statistics and UNIX tools. The presentation will also discuss why certain background processes must run in higher priority to maintain the application performance in RAC.

Presentation Name: A Kind and Gentle Introduction to RAC

Abstract: This session will introduce basic concepts such as cache fusion, conversion to RAC, protocols for interconnect, general architectural overview, GES layer locks, clusterware, etc. The session will also discuss the srvctl command and demo a few of these commands to improve the understanding.

Presentation Name: Parallel Execution in RAC

Abstract: This presentation will start to discuss and demo parallel server allocation, intra, and inter node parallelism aspects. The session will discuss the new parallelism features such as parallel statement queuing, parallel auto dop, and discuss the interaction of those features with RAC. The session will probe a few critical parameters to improve PQ performance in RAC.

Click here for more information or to register for RMOUG’s Training Days.

Posted in Oracle database internals, Performance tuning, Presentations, RAC | Tagged: , , | Leave a Comment »

Oracle Open World 2011 – My presentation on RAC topic

Posted by Riyaj Shamsudeen on September 28, 2011

I will be talking about “Administering Parallel Execution in RAC” with demos on Sunday morning 9AM-10AM (session id 28060). This is part of IOUG RAC SIG presentation series. You would enjoy the content and demos I have prepared.

I know, it is too early, but hoping to see you there!
BTW, if you have attended my RAC Advanced Troubleshooting class series, please don’t hesitate to introduce yourself when we meet.

Session details:
Session ID: 28060
Session Title: IOUG: Administering Parallel Execution in Oracle RAC
Venue / Room: Moscone West- 2005
Date and Time: 10/2/11, 9:00 – 10:00

Update: I just completed this session in IOUG. Thank you for coming, if you were in the room.
You can download the pdf file from
PX execution in RAC

Posted in 11g, Performance tuning, Presentations, RAC | Tagged: , , , , | 4 Comments »

RAC hack session – Tuesday – July 11 2011

Posted by Riyaj Shamsudeen on July 11, 2011

I will be conducting a 1-hour deep dive session about RAC LMS process (and about LGWR processes too if time permits) using advanced UNIX utilities. Read Tanel’s blog entry for details:
RAC hack session

See you there!

Posted in Performance tuning, Presentations, RAC | Tagged: , , , , , , , | 5 Comments »


Get every new post delivered to your Inbox.

Join 259 other followers