Did you know that there’s something like Active Session History also in the Exadata storage cells? ;-)
The V$CELL_THREAD_HISTORY view is somewhat like V$ACTIVE_SESSION_HISTORY, but it’s measuring thread activity in the Exadata Storage Cells:
Just a short notice to those interested that I’m very proud to be in the lineup for Enkitec’s Extreme Exadata Expo. The event takes place August 5-6, 2013 and is held in the Four Seasons Resort & Spa, Irving, Texas. There is plenty of time for you to register.
I was really sorry I missed out last year but this time I’m glad to participate and attend!
The list of great speakers includes too many to name here-you should see for yourself about who is coming to Dallas this August and why this event is unmissable.
I’m hoping to see you there!
This is yet another blogpost on Oracle’s direct path read feature which was introduced for non-parallel query processes in Oracle version 11.
For full table scans, a direct path read is done (according to my tests and current knowledge) when:
- The segment is bigger than 5 * _small_table_threshold.
- Less than 50% of the blocks of the table is already in the buffercache.
- Less than 25% of the blocks in the buffercache are dirty.
When an Oracle process starts executing a query and needs to do a full segment scan, it needs to make a decision if it’s going to use ‘blockmode’, which is the normal way of working on non-Exadata Oracle databases, where blocks are read from disk and processed by the Oracle foreground process, either “cached” (read from disk and put in the database buffercache) or “direct” (read from disk and put in the process’ PGA), or ‘offloaded mode’, where part of the execution is done by the cell server.
The code layer where the Oracle database process initiates the offloading is ‘kcfis’; an educated guess is Kernel Cache File Intelligent Storage. Does a “normal” alias non-Exadata database ever use the ‘kcfis’ layer? My first guess would be ‘no’, but we all know guessing takes you nowhere (right?). Let’s see if a “normal” database uses the ‘kcfis’ functions on a Linux x64 (OL 6.3) system with Oracle 220.127.116.11 64 bit using ASM.
This is just a very small post on how to watch the progress of the “CopyBack” state of a freshly inserted disk in an Exadata “Computing” (database) node. A disk failed in the (LSI Hardware) RAID5 set, and the hotspare disk was automatically used. The failed disk was replaced, and we are now awaiting the intermediate “CopyBack” phase.
The current state of the disks is visible using the following command:
As Exadata Storage Indexes (SI) are purely memory only structures located on the Exadata storage servers, care needs to be taken in how much memory they can potentially consume. As a result, there is a limit of 8 columns (or 8 SIs) that can be defined for a given 1M storage region at any point […]
Just a quick note to remind you that the call for papers for E4 is closing in a few days (on April 30). So if you have anything you think is interesting related to Exadata that you’d like to share we’d love to hear from you. By the way, you don’t have to be a world renowned speaker on Oracle technology to get accepted. You just need to have an interesting story to tell about your experience. Implementations, migrations and consolidation stories are all worthy of consideration. Any interaction between Exadata and Big Data platforms will also be of great interest to the attendees. Of course the more details you can provide the better.
Here’s a link to the submission page:
When using Locally Managed Tablespaces (LMT) with variable, system managed extent sizes (AUTOALLOCATE) and data files residing in ASM the Allocation Unit (AU) size can make a significant difference to the algorithm that searches for free extents.The corresponding free extent search algorithm when searching for free extents >= the AU size seems to only search for free extents on AU boundaries in order to avoid I/O splitting.Furthermore the algorithm seems to use two extent sizes when searching for free extents: A "desired" (for example 8MB) and a "minimum acceptable" (for example 1MB) extent size - however when performing the search the "desired" size seems to be relevant when limiting the search to free extents on AU boundaries.This can lead to some surprising side effects, in particular when using 4MB AUs.It effectively means that although you might have plenty o
I have not had a lot of time to post recently due to various reasons and a switch in jobs at Oracle. I currently am 100% dedicated to working in the Oracle Solution Center to help customers test the performance on Oracle’s engineered solutions. So, why am I sending this link?
Regardless of the performance tests that are performed, I often spend a fair amount of time showing the Availability aspects as well. Hopefully this video will help to demystify the availability aspects of Exadata.