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Oracle DBA






Oracle DBA - Oracle Optimization


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Checkpoint Tuning and Troubleshooting

This article provides the Database Administrator a better understanding of checkpoint processing and a description of four key initialization parameters used for checkpoint tuning.



Collecting Oracle Extended Trace (10046 event)

The most importing thing in collecting trace data is collecting properly scoped data. You should know the application and user interaction. Collecting too little data can point you in the wrong direction. Collecting data in the middle of a performance problem or long wait will give you a partial trace file missing some important information. The best time to collect is to turn tracing on, have a user start their process and turn tracing off after the process has completed.

Column Selections

As a DBA, one of the tasks that you will need to perform periodically is monitoring the number of chained rows in a table, as well as its fragmentation. If either or both of these become too high, you will need to reorganize that table to ensure that you have good performance.

Configure and use Oracle Enterprise Manager

This website features an overview of configuring and using Oracle Enterprise Manager. It includes a wealth of Oracle Resources extracted and updated frquently from the ODP.



Cost Based Optimizer (CBO) and Database Statistics

Whenever a valid SQL statement is processed Oracle has to decide how to retrieve the necessary data. This decision can be made using one of two methods: * Rule Based Optimizer (RBO) - This method is used if the server has no internal statistics relating to the objects referenced by the statement. This method is no longer favoured by Oracle and will be desupported in future releases. * Cost Based Optimizer (CBO) - This method is used if internal statistics are present. The CBO checks several possible execution plans and selects the one with the lowest cost, where cost relates to system resources. If new objects are created, or the amount of data in the database changes the statistics will no longer represent the real state of the database so the CBO decision process may be seriously impaired. The mechanisms and issues relating to maintenance of internal statistics are explained below:

Cost Control: Inside the Oracle Optimizer

Designing new applications for the Oracle Cost-Based Optimizer? Here's the latest information about how it works. This article has the following sections: Part 1 - Using SQL CBO Parameters Part 2 - Using CBO statistics Part 3 - Proper SQL development environment Part 4 - Using histograms to tune SQL Part 5 - Clustering and SQL tuning Part 6 - External costs and SQL execution Part 7 - Using hints to tune SQL Part 8 - Locating sub-optimal SQL

Database Benchmarking

If you have seen advertising literature from major database system vendors, invariably you have seen statements about how that database performed against other systems (benchmark results). All of the major vendors support and participate in benchmarking tests because, to some degree, they have to. The mindset must be along the lines of "Everyone else is doing it, so we'd look odd not participating in the tests ourselves - even though most analysts agree the tests are somewhat artificial and flawed."

Database block size = File system buffer size

Although there is every reason not to use buffered I/O (more) if you are constrained to do so for political reasons, it is important to ensure that the database block size matches the file system buffer size exactly. Here's why.

Faster Performance Using Oracle8 Stored Procedures

As objects such as stored procedures and triggers become more popular, more application code will move away from external programs and into the database engine. Oracle has been encouraging this approach in anticipation of the object-oriented features of Oracle Version 8. However, the Oracle DBA must be conscious of the increasing memory demands of stored procedures, and carefully plan for the days when all of the database access code resides within the database.

Inside the Oracle SGA Regions

Most DBAs know all about the Oracle System Global Area (SGA). The SGA is Oracle's structural memory area that facilitates the transfer of data and information between clients and the Oracle database. Long gone are the days when only four main tunable components existed.

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Oracle DBA

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SQL Statement Tuning
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Oracle DBA FAQ