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MV Refresh

I have a fairly strong preference for choosing simple solutions over complex solutions, and using Oracle-supplied packaged over writing custom code – provided the difference in cost THere’(whether that’s in human effort, run-time resources, or licence fees) is acceptable. Sometimes, though, the gap between simplicity and cost is so extreme that a hand-crafted solution is clearly the better choice. Here’s an idea prompted by a recent visit to a site that makes use of materialized views and also happens to be licensed for the partitioning option.

EM12c Enterprise Monitoring, Part V “Warning Management”

This is Part IV in a multi-part series, demonstrating how to take EM12c from out of the box to enterprise level.  

Parallel Execution

While checking out potential scalability threats recently on a client system, I was directed to a time-critical task that was currently executing the same PL/SQL procedure 16 times (with different parameters) between 6:00 and 7:00 am; as the system went through its next phase of expansion the number of executions of this procedure was likely to grow. An interesting detail, though, was that nothing else was going on while the task was running so the machine (which had 6 cores) was running at 16% CPU.

An obvious strategy for handling the required growth target was to make sure that four (possibly 5) copies of the procedure were allowed to run concurrently. Fortunately the different executions were completely independent of each other and didn’t interfere with each other’s data, so the solution simply required a mechanism to control the parallelism. Conveniently 11gR2 gave us one.

VirtualBox 4.2.18 Released…

VirtualBox 4.2.18 was released a little over a day ago. Not sure how I missed that one… :)

The downloads and changelog are in the usual places. Happy upgrading!



Hash Joins

I’ve written notes about the different joins in the past – but such things are always worth revisiting, so here’s an accumulated bundle of comments about hash joins.

Oracle IO on linux: database writer IO and wait events

This post is about database writer (dbwr, mostly seen as dbw0 nowadays) IO.
The testenvironment in which I made the measurements in this post: Linux X64 OL6u3, Oracle (no BP), Clusterware, ASM, all database files in ASM. The test environment is a (VMWare Fusion) VM, with 2 CPU’s.

It might be a good idea to read my previous blog about logwriter IO.

The number of database writers is depended on the number of CPU’s visible to the instance (when not explicitly set with the DB_WRITER_PROCESSES parameter), and seems mostly to be CEIL(CPU_COUNT/8). There might be other things which could influence the number (NUMA comes to mind). In my case, I’ve got 2 CPU’s visible, which means I got one database writer (dbw0).

EM12c Enterprise Monitoring, Part IV

This is Part IV in a multi-part series, demonstrating how to take EM12c from out of the box to enterprise level.  

I will be speaking at Oracle OpenWorld and Strata + HadoopWorld NY

I will be speaking at a few more conferences this year and thought to add some comments about my plans here too. Here’s the list of my upcoming presentations:

Oracle Performance & Troubleshooting Online Seminars in 2013

In case you haven’t noticed, I will be delivering my Advanced Oracle Troubleshooting and Advanced Oracle Exadata Performance: Troubleshooting and Optimization classes again in Oct/Nov 2013 (AOT) and December 2013 (Exadata).

I have streteched the Exadata class to 5-half days as 4 half-days wasn’t nearly enough to deliver the amount of details in the material (and I think it’s still going to be a pretty intensive pace).

And that’s all for this year (I will write about conferences and other public appearances in a separate post).


EM 12c Snap Clone

Oracle OEM 12c introduces a new feature that enables the creation of Oracle database thin clones by leveraging file system snapshot technologies from either Oracle ZFS Storage Appliance or Netapp.  The OEM adds a graphic interface to the process of making database thin clones. The feature that enables database thin cloning in OEM is called Snap Clone and is part of OEM’s Cloud Control Self Service for data cloning. Snap Clone is available via the feature Database as a Service (DBaaS). Snap clone leverages the copy on write technologies available in some storage systems for database cloning.  Support is initially available for NAS storage and specifically on Oralce ZFS Storage Appliacen and NetApp Storage.