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Oracle performance tuning - an update

Oracle performance tuning – an update

A tutorial is now available to perform Oracle performance tuning of applications and SQL statements. This tutorial has been expanded to include case studies, which will go a long way in better understanding of concepts explained. Link to the PDF tutorial here: Tuning.pdf This current posting is an extension to the existing post on performance […]

Oracle: Snapshot too old?

Oracle: Snapshot too old?

Okay, so you have received the Oracle error ORA-01555 Snapshot Too Old and have no clue how to go about resolving it? This post is made for you then. (The first time an application developer has written about this rather than a DBA.) First, why does this occur? When you run a query, Oracle retains […]

Oracle deadlocks: the what and the how

Oracle deadlocks: the what and the how

Everyone knows what a deadlock is: a situation in which two or more competing processes are waiting for the other to finish, and thus neither ever does. The purpose of this post is to help people understanding the deadlock a little better with a view to enable them to fix the problem when they find […]

When NOT to normalise the database

When NOT to normalise the database

When talking of Database Normalisation, textbooks often talk of BCNF, fifth and higher normal forms. However, in practice (in large software/ERPs) I have rarely noticed normalisation beyond Third Normal form. In fact, there is a certain degree of redundancy that is desirable. While doing database design, I believe there are two critical aspects that should […]

Generating sequential numbers in a database

Generating sequential numbers in a database

You are creating an application that allows organisations to manage employees. One of the tasks that it has to do is generate an employee ID when a new employee is being entered. One way of doing this is through this query: SELECT max(empl_id)+1 FROM employee; However, this query presents a problem in a multiuser environment: […]

Performance tuning SQL queries in Oracle

Performance tuning SQL queries in Oracle

Video tutorial showing how to optimise your SQL queries for maximum performance. Talks about indexes, statistics, hints and optimiser plans.