12c

oraclebase's picture

Multitentant (Pluggable Database) Videos

It’s been over 2 years since 12c was released and there still seems to be a lot of confusion about the pluggable database stuff. I think most people know the top-level concept, there’s only so many times you can see the memory stick analogy before it gets burned on your skull, but that doesn’t do much to help with the reality of working with it day-to-day.

Jonathan Lewis's picture

PL/SQL Functions

Assuming everything else has been tuned to perfection, what’s the best you can do while calling PL/SQL functions from SQL ? Here’s a little code to create a table with some data, and a function that we can use to start an investigation:

oraclebase's picture

PDB Logging Clause… Again…

About 14 months ago I spotted a problem with the PDB Logging Clause. I opened an SR and several months later I got a patch, which unfortunately didn’t fix the issue, just altered the symptom somewhat. I wrote about that patch here.

Yesterday I got a new patch, which actually does fix the problem, so now the PDB Logging Clause works as documented!

I’ve updated the PDB Logging Clause article to reflect the change.

Jonathan Lewis's picture

Result Cache 2

Following on from my earlier posting of problems with temporary table and the PL/SQL result cache (a combination which the manuals warn you against) here’s another problem – again, to a large degree, self-inflicted.

Imagine you have a complex report involving a large number of financial transactions with a need to include calculations about current exchange rates. Unfortunately the rules about calculating the appropriate exchange rate for any transaction are complex and you find you have a choice between adding 6 tables with outer joins and a couple of aggregate (max) subqueries to the base query or calling a PL/SQL function to calculate the exchange rate for each row. I’m going to create an extremely simplified model of this requirement:

Jonathan Lewis's picture

Result Cache

Yesterday I thought I’d spend half an hour before breakfast creating a little demonstration of a feature; some time about midnight I felt it was time to stop because I’d spent enough time chasing around a couple of bugs that produced wrong results in a variety of ways. Today’s short post is just little warning: be VERY careful what you do with the PL/SQL result cache – if you use the results of database queries in the cache you may end up with inconsistent results in your application. Here’s one very simple example of what can go wrong, starting with a little script:

Richard Foote's picture

Index Advanced Compression: Multi-Column Index Part I (There There)

I’ve discussed Index Advanced Compression here a number of times previously. It’s the really cool additional capability introduced to the Advanced Compression Option with 12.1.0.2, that not only makes compressing indexes a much easier exercise but also enables indexes to be compressed more effectively than previously possible. Thought I might look at a multi-column index to highlight just […]

Jonathan Lewis's picture

IN/EXISTS bugs

Here’s a simple data set – I’m only interested in three of the columns in the work that follows, but it’s a data set that I use for a number of different models:

Jonathan Lewis's picture

Index Usage – 2

I’ve been a little slow in the follow-up to my previous posting on possibly redundant indexes. Before going into the slightly more complex stuff, there’s another peripheral point (but a very important one) that’s worth raising about how clever the optimizer can be. Here’s some code for 11.2.0.4 to demonstrate the point:

oraclebase's picture

Adaptive Query Optimization in Oracle 12c : Ongoing Updates

I’ve said a number of times, the process of writing articles is part of an ongoing learning experience for me. A few days ago my personal tech editor (Jonathan Lewis) asked about a statement I made in the SQL Plan Directive article. On further investigation it turned out the sentence was a complete work of fiction on my part, based on my misunderstanding of something I read in the manual, as well as the assumption that everything that happens must be as a result of a new feature. :)

oraclebase's picture

Fedora 22/23 and Oracle 11gR2/12cR1

linux-tuxAs always, installations of Oracle server products on Fedora are not a great idea, as explained here.

I was reading some stuff about the Fedora 23 Alpha and realised Fedora 22 had passed me by. Not sure how I missed that. :)

Anyway, I did a run through of the usual play stuff.

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