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Oracle Tips by Burleson

Choosing a Database Block Size

• Use database block sizes of 16K and 32K for data warehouses and decision support systems.  Decision support systems and data warehouses, by their nature, access large volumes of data to provide users with the information required to make business decisions.   You will reduce disk I/O by storing more data in each block.

The Oracle Database Fundamentals I (1Z0-031) and the Oracle Database Performance Tuning (1Z0-033) certification tests will have a few questions on database blocks.  Test candidates should know:

• The db_block_size parameter
   

• How to specify non standard block sizes in Oracle9i
   

• What tablespaces must use the default Oracle block size
   

• How to change the default Oracle block size
   

• The contents of an Oracle block
   

• What affect the PCTFREE and PCTUSED parameters have on data block free space
   

• The differences between PCTFREE/PCTUSED and automatic segment space management
   

• What row chaining and row migration are and the affect they have on database performance
   

• How to correctly size the default Oracle block size
   

For more details and scripts, see my new book " Oracle Tuning: The Definitive Reference", over 900 pages of BC's favorite tuning tips & scripts.  You can buy it direct from the publisher for 30%-off and get instant access to the code depot.