Prior to Oracle9i, the size of the System Global Area (SGA) was static and changing it would require a restart of the Oracle instance. This used to pose a number of problems for DBAs who would like to change the SGA size as needed by the application without worrying about downtime. This is particularly true for Oracle DBAs responsible for e-businesses. For an e-business, minimizing downtime is probably the most important requirement, and Oracle DBAs need to look for innovative ways to achieve this objective.
With a static SGA, it becomes very difficult to react to changing application demands, especially if you have not performed proper capacity planning. Oracle9i allows the SGA size to be changed dynamically by using the ALTER SYSTEM command.
This article is the first in a three-part series that discusses the SGA enhancements available with Oracle9i. The following topics will be covered by the articles:
Part 1: Working with multiple block sizes (this article)
Part 2: Sizing the database cache
Part 3: Auto-tuning using the server parameter file (SPFILE)