Mohammed Abdul Afroze

• Nov 1st, 2007

 

Since the inception of Oracle, the System Global Area (SGA) has been static.
In Oracle8i Database Administrators (DBAs) do not have any control over the
SGA size once the instance is started. Oracle9i allows a DBA to modify the SGA
size dynamically. This provides an SGA that will grow and shrink in response to
a DBA command.

This feature implements an infrastructure to allow the Oracle server to change
the SGA configuration without shutting down the instance. The Oracle Server
can modify the physical address space use to respond to the operating system's
use of physical memory.

Beginning with Oracle9i, the dynamic SGA infrastructure will allow for the
sizing of the Buffer Cache, Shared Pool and the Large Pool (see note below)
without having to shutdown the database.

The dynamic SGA infrastructure also allows the limits to be set at run time on
how much physical memory will be used for the SGA. The instance will be started
under-configured and will use as much memory as the operating system gives it.