BASIC table compression: use with care


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

Controlling Administrator Access with Oracle Database Vault “Separation of Duty”

This paper provides best practices for rapid deployment of Oracle Database Vault protections to
secure sensitive application data inside the database. Oracle Database Vault enables you to restrict administrative access to an Oracle
database. This helps you address the most difficult security problems remaining
today: protecting against insider threats, meeting regulatory compliance
requirements, and enforcing separation of duty. It covers the following main topics:

How and why to quiesce the database


The ability to quiesce the database was introduced in release 9, but to this day I find that many people are not aware of it. It can be really useful - so let's describe it. I'll begin by positioning the quiesce capability: when is it useful. Then detail how to do it, then reverse engineer the mechanism.

Book review: Brian Peasland, Oracle RAC Performance Tuning


Excellent book - I've just posted this review on Amazon:

Identifying missing FK indexes


Why publishing this under SQL instead of RDBMS Server?

The necessaty to create supporting indexes for foreign keys has been explained in other articles.
However writing a foolproof query to identify missing FK indexes is not so straightforward as it might look. I used to do it PLSQL, but this has proven not to scale very well and taking quite some elapsed time and system resources in databases with many thousands of tables. The blog entry is about the challenge to get the job done with a well performing SQL statement.

Tuning SQL with dynamic sampling


Another example of what I think of as "the self-tuning database". Setting optimizer_dynamic_sampling=11 can fix many performance problems, without the DBA needing to use his brain at all.

Book review: Kevin Meade, Oracle SQL Performance Tuning and Optimization


Excellent exposition of a very effective SQL tuning metodology

Oracle External Tables


 The Oracle external tables feature allows us to access data in external sources as if it is a table in the database.
 External tables are read-only.
 No data manipulation language (DML) operations is allowed on an external table.
 An external table does not describe any data that is stored in the database.

Hash join anti vs Nested loop join anti

This post shows you details about a specific case where 'hash anti join' is defeated by 'nested loop anti join'.
The initial problem came to light in a very large BW system running on Oracle when several BW loads (making use of older data in the BW system) reported missing dimension ids in the dimension tables.

Redo and undo volumes - take two


Following a question on OTN I did another test on redo and undo, just to prove that frequent COMMIT can be bad for performance. The results surprised me. I expected that row-by-row commit would be worse then a single commit at the end of a multi-row transaction, but I hadn't expected it to be this bad. As well as being much slower, both undo and redo volumes are vastly greater.


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