John Watson's blog

Oracle 12cR2 - the next release, cloud only?

articles: 

We are all waiting for database release 12.2 - but you won't get it on your own hardware.

How indexes can degrade performance

articles: 

Indexes may improve the performance of SELECT statements, but what about DML? This simple demo shows how bad they can be.

Roles , PL/SQL, and ORA-00942: table or view does not exist

articles: 

Many developers find that their code fails with ORA-942, but when they test the failing statement from the SQL> prompt, it works. Why, and what can you do to fix it?

Partitioning and Oracle Standard Edition

articles: 

I first came across partitioning with release 7, when it didn't exist. Like many DBAs, I simulated it by writing a lot of application code. You can still do this – and you may have to if you haven't bought Enterprise Edition plus the partitioning option. Here's another way to do it, with partitioned views.

When is an index access path better than a full table scan?

articles: 

The cost based optimizer makes decisions that can be hard to understand. One of the hardest may be why it chooses indexed or scan access paths: a burning question for many DBAs.

What is DB Time? Where has it gone?

DB Time is the time spent by the database server executing user calls. What is this composed of? CPU time, waiting time, and IO time.

Proxy authentication

articles: 

Proxy authentication has been around since release 9i, but it isn't widely used. It can be a very useful facility for giving certain users access to high privileges without having to give them any direct grants or roles, and avoids many of the problems of using shared accounts. It is of course fully audited.

Standard Edition release 12.1.0.2: licensing...

articles: 

Standard Edition release 12.1.0.2 is now available. Download it from the usual locations. But along with the great news, comes some news that is not so great: the licensing model has changed.

ADVANCED table compression: an improvement

articles: 

Following previous blog re BASIC compression, here are a couple of simple tests with Advanced Compression - which is supposed to survive conventional DML.

BASIC table compression: use with care

articles: 

BASIC table compression is included with Enterprise edition, and can achieve respectable compression ratios. But beware! Subsequent DML may be disastrous.

Pages

Subscribe to RSS - John Watson's blog