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.
The basic idea behind the Exadata Hybrid Columnar Compression (hereby referred as EHCC) is to reprise the benefits of column based storage while sustaining to the fundamental row based storage principle of Oracle database. Oftentimes the databases following column based storage claim that comparatively they needs less IO to retrieve (more...)
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 (more...)
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 (more...)
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 (more...)
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, (more...)
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 (more...)
Exadata Article as NYOUG's Article of the Year 2012
The Editors of New York Oracle User Group (NYOUG)
publication - TechJournal - chose my article Exadata Demystified
as the Article of the Year
. Here is the snippet from the Editorial:
And the Award Goes To …
The Editor’s Choice Award (more...)
With Exadata version 126.96.36.199.0 came the Unbreakable Linux Kernel for Exadata, which had been the stock EL5 redhat kernel prior to this version (2.6.18). With the unbreakable kernel came the opportunity to run the perf utility. This utility has the opportunity to see which (more...)
Ein Praxistest überzeugt leichter, als lange Erklärungen. Daher stellt der Oracle
VAD Azlan Deutschland nun eine Oracle Exadata Demomaschine für Reseller bereit.
Händler und unabhängige Software Hersteller (ISVs) können
sie sowohl für Teststellungen direkt vor Ort bei Endkunden als auch zum Testen
eigener Applikationen nutzen. Für Partner bietet das den (more...)
I will be doing a lot of (Exadata) talking and teaching in the coming months. Here’s a list of events where you’ll see me speaking, teaching, hacking, learning and hopefully also drinking beer:
In order to look how Exadata smartscans are different, first let’s have a peek the Oracle full segment/multiblock read evolution as short as possible:
a) Traditional multiblock reads, visible via the event ‘db file scattered read’
The essence is: Multiple adjacent blocks are read from disk, and put in the (more...)
Exklusiv für Oracle
Partner: Produkt- und Geschäftsstrategien, Fallstudien, Kundenerfolge, Erfolgreiche
- The trend to clustered computing is sustainable.
- The trend to appliances is also sustainable.
- The “single” enterprise cluster is almost as much of a pipe dream as the single enterprise database.
I shall explain.
Arguments for hosting applications on some kind of cluster include:
If you attended my Exadata hacking session today, you saw me using the cellver.sql script which lists some basic configuration info about the currently connected storage cells:
Show Exadata cell versions from V$CELL_CONFIG....
CELLNAME CELLSRV_VERSION FLASH_CACHE_MODE CPU_COUNT UPTIME KERNEL_VERSION MAKE_MODEL
-------------------- -------------------- -------------------- ---------- (more...)
When the question of what starts OSWatcher (OSW) on Exadata was raised at a client site and I thought I’d take a quick look. It took me a little longer than I expected to work out the detail and therefore it seems worth sharing.
If you’re simply looking to change the “snapshot interval”, “archive retention” or “compression command” then /opt/oracle.cellos/validations/init.d/oswatcher is what you need to modify and you’ll find a line with ./startOSW.sh X Y Z. Where X is the snapshot interval, Y is the archive retention and Z is the compression command used to compress the (more...)