Blogs

How and why to quiesce the database

articles: 

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

articles: 

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

Identifying missing FK indexes

articles: 

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

articles: 

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

articles: 

Excellent exposition of a very effective SQL tuning metodology

Oracle External Tables

articles: 

 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 11.2.0.4 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

articles: 

Following a question on OTN https://community.oracle.com/message/12801175 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.

Software Review - Stellar Phoenix Oracle Database Recovery Software

The demand of Oracle database is very high and because of high demand, its security becomes the most concerned part of its users. Backup is the initial process you can do for your database security. However, at times, taking backup is also not sufficient and issues like backup file corruption, database damage due to virus, etc. takes place and data loss occurs. Therefore it's always better to have a utility to repair your damaged or corrupt Oracle Database Files and reconstruct its objects.

V$RESERVED_WORDS & X$KWDDEF - Interesting facts!

articles: 

It's a lazy Friday and I saw an interesting question in Stack Overflow about "Why are there two “null” keywords in Oracle's v$reserved_words view?" And I spent next 2 hours digging into knowing the reason. Here are my findings:

We need to understand how to interpret the view v$reserved _words. To determine whether a particular keyword is reserved in any way, check the RESERVED, RES_TYPE, RES_ATTR, and RES_SEMI columns.

Pages

Subscribe to RSS - blogs