Database Blog

  • Oracle In-memory Database—Speed and Simplicity Meet Up. Have you tried it out yet?

    Dec 19, 2013

    Reading Time: 2 minutes One of the major announcements Oracle made during the Open World was the launch of Oracle In Memory Database Option. The In-Memory option to Oracle Database 12c is 100 percent compatible with existing applications and leverages all existing Oracle Database functionality. At first look, some key benefits jump out: Though this is a paid option, it promises a high ROI It takes just one change in parameter to turn it on From published information, it…..

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  • Query Rewrite: What is MySQL Doing To My Queries?

    Nov 30, 2011

    Reading Time: < 1 minute The Impact of Query Rewrite on MySQL Query Optimization When processing a query, every relational database vendor takes a number of similar steps to parse, validate, and optimize a query. MySQL does the following: Validates the query syntax — does it use valid operators, are the clauses in the proper order, etc. Validates the query semantics — are the the objects (tables, views, columns) valid database objects in the database, etc. Transforms the query —…..

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  • Why I Avoid Database Hints: a followup

    Jun 21, 2011

    Reading Time: < 1 minute In an earlier blog post about database hints, I gave a number of reasons why I dont like to use hints in SQL queries. Today I wanted to follow up to share one situation where I think hints are OK, even necessary. As described very well in an article in an article by Andrew Kelly in SQL Server Magazine (InstantDoc 129916),  hints are sometimes necessary when we wish to minimize logging during bulk loading operations……

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  • Five Leading Causes of Oracle Database Performance Problems

    Feb 3, 2011

    Reading Time: < 1 minute As we evaluate our clients’ Oracle databases and help them solve problems relating to performance and stability, we see many causes for these issues. However, there are a small number of basic issues that tend to cause problems on the majority of systems. Our Tech Tips document describes these issues and discusses methods of identifying them and resolving them. Topics include: Statistics Gathering Sga Sizing Redo Log Sizing Index Usage Extent Management Download Top 5 Oracle Performance Tuning…..

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  • Oracle Performance Tuning — Trust but Verify

    Nov 18, 2010

    Reading Time: 2 minutes During an Oracle Performance Tuning engagement in the past, I learned a valuable lesson about validating the information that you are given during a database evaluation. About ten years ago, a client called me with a serious problem. They had just completed development on a new Oracle application at a large pharmaceutical company and the new system had been in production for a week or two. They could not understand why performance had degraded so…..

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  • Oracle Performance Tuning: Periodically reorganize database objects

    Oct 21, 2010

    Reading Time: < 1 minute One of our Oracle Consultants shared a story with me today that illustrates the importance of periodically reorganizing objects in an oracle database. He was examining a performance problem with a very small oracle table. The table had only 154 rows!. Hardly a large table, and yet it was taking over a minute to do a full table scan. After some investigation, he found that in the past the table had over a million rows……

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  • Oracle Performance Tuning — Log Sync Waits

    Aug 5, 2010

    Reading Time: 3 minutes I recently worked with a client to resolve a significant performance issue related to painfully slow queries in an Oracle database. One of the queries that they wished to execute was taking over five hours to run. This is an Oracle 10g database running on a Solaris platform. The server has 8 processors so there is plenty of processing power. The database is very large with a very high insertion rate. The database is about…..

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  • Five reasons why I avoid database query hints

    Jul 28, 2010

    Reading Time: 2 minutes I know that some will disagree with me on this but I have never been a fan of database query hints. Most database vendors give you the ability to override the query optimizer with hints that you specify in a query. Each query can be executed in a variety of ways by the database engine. Normally, the optimizer evaluates the statistics about the data in each of the tables involved in the query and makes…..

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