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Oracle

Predicate Order

A recent OTN post demonstrated a very important point about looking at execution plans – especially when you don’t use the right data types. The question was:

We’ve this query which throws invalid number

SELECT * FROM table A
WHERE A.corporate_id IN (59375,54387) AND TRUNC(created_dt) BETWEEN '19-DEC-14' AND '25-DEC-14';

However it works fine if we use not in instead of in

SELECT * FROM table A  
WHERE A.corporate_id  NOT IN (59375,54387) AND TRUNC(created_dt) BETWEEN '19-DEC-14' AND '25-DEC-14';

Please assist.

Databases Running in the Cloud

cloudI’ve been playing around with running databases in the cloud recently. It’s quite simplistic stuff, just to get a feel for it and investigate the possibilities of using it for some projects at work. Here’s what I’ve got so far.

SLOB 2.3 Is Getting Close!

SLOB 2.3 is soon to be released. This version has a lot of new, important features but also a significant amount of tuning in the data loading kit. Before sharing where the progress is on that front, I’ll quickly list some of the new important features that will be in SLOB 2.3:

Oracle : Do you even internet? (broken links again)

Broken-LinkI mentioned in a recent post that Oracle are often guilty of changing URLs, which breaks all the documentation links in your site. Someone replied with this link. I knew I had a lot of clean-up to do, but I expected most of it to be old URLs, like stuff pointing to 8i, 9i etc.

I’ve just been looking and vast swathes of links have been changed in the 12.1 docs. In some cases, articles I wrote a couple of weeks ago are screwed. The reference manual is guilty of this big time!

Lab Report: Oracle Database on EMC XtremIO. A Compression Technology Case Study.

If you are interested in array-level data reduction services and how such technology mixes with Oracle Database application-level compression (such as Advanced Compression Option), I offer the link below to an EMC Lab Report on this very topic.

To read the entire Lab Report please click the following link:   Click Here.

The following is an excerpt from the Lab Report:

Executive Summary
EMC XtremIO storage array offers powerful data reduction features. In addition to thin provisioning, XtremIO applies both deduplication and compression algorithms to blocks of data when they are ingested into the array. These features are always on and intrinsic to the array. There is no added licensing, no tuning nor configuration involved when it comes to XtremIO data reduction.

EM Express versus EM Cloud Control

Recently I was asked the question “What is the real difference between EM Cloud Control [NOTE: I’ll refer to this as EM12c through the rest of this post] and EM Database Express in 12c?” It was (for me) a pretty easy question to answer, but I wanted to provide the questioner with a link to the place in the Enterprise Manager documentation where it covers that in detail. Somewhat to my surprise, I wasn’t able to find such a link – well, not quickly anyway. I think the reason for that is the documentation for EM Express (as it’s more commonly abbreviated to) falls under the database documentation which is owned by a different group in Oracle than the Enterprise Manager documentation. Well, that’s my speculation anyway. It may just be there in the documentation and I couldn’t find it in my quick search.

Understanding SQL

From time to time someone publishes a query on the OTN database forum and asks how to make it go faster, and you look at it and think it’s a nice example to explain a couple of principles because it’s short, easy to understand, obvious what sort of things might be wrong, and easy to fix. Then, after you’ve made a couple of suggestions and explained a couple of ideas the provider simply fades into the distance and doesn’t tell you any more about the query, or whether they’ve taken advantage of your advice, or found some other way to address the problem.

Such a query, with its execution plan, appeared a couple of weeks ago:

Installing Enterprise Manager 12c For Testing

A question I get asked fairly often when I’m at conferences, either during the Q&A for my sessions or in general chit chat (a.k.a. networking) afterwards is “I want to play around with the features in Enterprise Manager 12c but don’t want to do that in our Production environment. How do I go about installing a copy of Enterprise Manager 12c somewhere else in the easiest way as a test environment?” The answer to that is pretty straightforward. It’s to download the relevant VM template from Oracle’s Software Delivery Cloud. Note: The screenshots shown in this post are from the new and enhanced Oracle Software Delivery Cloud, rather than the classic Software Delivery Cloud, so if you use the classic form your screens will be different. On the first screen, make sure you understand the export restrictions and click “Accept”:

SQL ID Specific Performance Information

When you need to have information about one SQL_ID and don’t need everything and the kitchen sink, there are a few different ways to collect this via Oracle.  I’m surprised how rarely this is covered in performance tuning/optimization, (whatever the current “acceptable” term is for fixing a database when there are performance issues arise… J)  classes, manuals and documentation.

Migrated rows

I received an email recently describing a problem with a query which was running a full tablescan but: “almost all the waits are on ‘db file sequential read’ and the disk read is 10 times the table blocks”.  Some further information supplied was that the tablespace was using ASSM and 16KB block size; the table had 272 columns (ouch!) and the Oracle version was 11.2.0.4.