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Category Archives: Internals

One of the things you just need to know about Oracle …

A couple of years ago I did ask my developers to start using the varchar2(char) option when creating new tables. In Norway we have some characters in the alphabet (‘Æ’, ‘Ø’, ‘Å’) that uses more than 1 byte of storage (when the database characterset is set to AL32UTF8). Using the default – varchar2(byte) – could then decrease the number […]

Posted 17 March 2016 † Lasse Jenssen § Database Design § DBA § Performance ‡ Comments (0) °

Oracle 11g: New Locking behavior (modes) … an unexpected behavior. Or?

I just noticed some strange locking behavior in one of our production databases. It took me a while to reproduce this in test. I’ve based my example on Richard Foots blog “Oracle11g: New Locking Modes When Policing FK Constraints (A Wolf at the Door)”.

Posted 14 January 2015 † Lasse Jenssen § 11g New Feature § Database Design § Performance § SQL ‡ Comments (0) °

Isolation Levels by Tom Kyte

I just reread the Oracle Magazine article by Tom Kyte named “On Transaction Isolation Levels” from November 2005. Great article that really explains why your relational database can not be treated as a black box. From the article: “The ANSI/ISO SQL standard defines four levels of transaction isolation, with different possible outcomes for the same […]

Posted 25 June 2014 † Lasse Jenssen § Oracle ‡ Comments (0) °

Oracle foreign key ≠ referential integrity

I used to believe that implementing a foreign key in Oracle enforced referential integrity. Until today! Until reading this article by Tom Kyte, showing that this isn’t necessarily the truth. And I don’t think very many is aware of this. Yes – it does involve foreign keys allowing NULL values, but is’t that rather common?

Posted 20 June 2012 † Lasse Jenssen § Database Design § Oracle ‡ Comments (0) °

Notes on blockdumps reading “Oracle Core” (by Jonathan Lewis)

First of all – This book (Oracle Core – by Jonathan Lewis) is great if you really want to know the Oracle internals. And who doesn’t??? It does take some effort reading, but considering the content it’s very well written. Finally I can throw away my old compendium (from same author – Jonathan Lewis) which […]

Posted 14 January 2012 † Lasse Jenssen § Oracle ‡ Comments (0) °