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April 2015

Whitepaper: Oracle Database 11g and 12c Consolidation and Workload Scalability with EMC XtremIO 3.0

This is a just a quick blog post to direct readers to the best Oracle-related paper detailing the value EMC XtremIO brings to Oracle Database use cases.  I’ve been looking forward to the availability of this paper for quite some time as I supported (minimally, really) the EMC Global Solutions Engineering group in this effort. They really did a great job with this testing! I highly recommend this paper for readers who are interested in:

Not Exists

This whole thing about “not exists” subqueries can run and run. In the previous episode I walked through some ideas of how the following query might perform depending on the data, the indexes, and the transformation that the optimizer might apply:

Eventual Consistency is NOT a violation of the relational model (says C. J. Date)

C. J. Date was kind enough to comment on my article in the last issue (February 2015) of the NoCOUG Journal (see The Rise and Fall of the NoSQL Empire ). The full text of his remarks will be published in the next issue (May 2015). Here’s a sneak preview:
First, to say that a database (distributed or otherwise) is consistent merely means, formally speaking, that the database conforms to all stated integrity constraints. Now, it’s crucially important that databases always be consistent...(read more)

How to pass the #Oracle Database 11g OCM Exam

The Oracle Certified Master Exam is among the highest rated exams in the IT industry for a good reason: It is extremely hard to pass!

Unlike most other IT exams that are done as multiple choice tests, the OCM exam means two days of  hands-on practical tasks. No chance you can pass it by just reading books or brain dumps and learning by heart without deep understanding. Without years of practical experience with Oracle database administration – don’t even think about it. Even as a seasoned DBA, you won’t find it easy to pass the OCM exam. Why is that so?

Data Subsetting

Recently a good friend of mine posted his thoughts on data subsetting. As you would expect from Kyle, it’s a well-reasoned discussion (well, till he went down the path of using Delphix </p />
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ASH Data and How Sizing an AWR Warehouse Can be Mitigated

When sizing the AWR Warehouse, one of my requirements is to have certain reports for a sampling of databases that will source the AWR Warehouse. This report provides me the right information to create the correct sizing requirements vs. any assumptions done with other choices.

temporary undo in 12c

This feature seems a no-brainer once you’re on 12c. After all, why would you want your global temporary tables to be hammering away at your redo logs.  With that in mind, my initial tinkering with the feature had me getting ready for a “blog rant” because it did not seem to work.  Let’s see how you might end up unimpressed. 

Here’s the standard usage of undo (as per 11.2 and below).

 

No Local Oracle User Group? Oh Well, Go to a Bar…

Is there no local Oracle user group in your area? Do you wish you could share experiences with like-minded people? Is there no opportunity to talk about the technology you work with? Do you feel you would benefit from expanding your network of friends and contacts? But without a local user group it’s really hard to do any of that! – At least face-to-face. And, let’s face it, meeting for real really does beat meeting on-line. I know, you are sad about it.

Well, go to a bar. Have a drink, it might make you feel better. Especially if you go with Dave in your team. Ask your friend across town along who also works with Oracle Tech. And maybe she could bring her friend who is an Oracle DBA too.

Well done! You now have an Oracle User Group!

Enabling Edition Based Redefinition On A Schema With Object-Relational Tables

This is just a heads-up for those thinking about using Edition Based Redefinition (EBR) and enabling it on an existing schema with objects. Although EBR isn't exactly a new feature its current adoption level is probably not that high (which probably changes in future as Oracle E-Business Suite uses EBR now as part of their default upgrade procedure as far as I understood).I was recently contacted by someone who enabled EBR on an existing schema using ALTER USER ... ENABLE EDITIONS and had to use the "FORCE" option since there were (according to the official ALTER USER documentation) "objects that are not editionable and that depend on editionable type objects in the schema. ...

Not Exists

Another question on a seemingly simple “not exists” query has appeared on OTN just a few days after my last post about the construct. There are two little differences between the actual form of the two queries that make it worth repeating the analysis.

The first query was of the form:


select from big_table
where  not exists (select exact_matching_row from small table);

while the new query is of the form: