Oracle9i provides a number of enhancements in regards to the SGA that can be used by Oracle DBAs. E-businesses place a very strict condition for successminimal (if not zero) downtime of the system. The reason for this strict requirement is that the revenue of an e-business is directly related to the amount of time it spends up and running. In addition to the availability requirements, an Oracle DBA has to work with equally strict performance requirements. In an e-business, the business has to support a large number of users, with unpredictable system loads, and allow performance to be satisfactory for all users at all times.
Prior to Oracle9i, it was very difficult to plan for all these changing conditions and react to them without frequent downtimes for maintenance purposes. With Oracle9i, the SGA can be changed dynamically. This one enhancement allows the DBA to relax a little and prepare for various situations in a realistic manner. In addition, the Oracle DBA can now create tablespaces with different block sizes in the same database. Objects such as tables and indexes can now be created by considering their application usage, and subsequently these objects can be placed in a tablespace that has the appropriate block size.
The auto-tuning feature of Oracle9i can be used in single-instance Oracle9i databases as well as Oracle9i Real Application Clusters to allow Oracle to dynamically change the configuration parameters as needed to improve performance.