The PGA also includes a sort area. The sort area is used whenever a user request requires a
sort, bitmap merge, or hash join operation.
As of Oracle9i, the PGA_AGGREGATE_TARGET parameter, in conjunction with the
WORKAREA_SIZE_POLICY initialization parameter, can ease system administration by allowing
the DBA to choose a total size for all work areas and let Oracle manage and allocate the memory
between all user processes. As I mentioned earlier in this chapter, the parameter MEMORY_
TARGET manages the PGA and SGA memory as a whole to optimize performance.
Software Code Area
Software code areas store the Oracle executable files that are running as part of an Oracle instance.
These code areas are static in nature and only change when a new release of the software is installed.
Typically, the Oracle software code areas are located in a privileged memory area separate from
other user programs.
Oracle software code is strictly read-only and can be installed either shared or non-shared.
Installing Oracle software code as sharable saves memory when multiple Oracle instances are
running on the same server at the same software release level.
Background Processes
When an Oracle instance starts, multiple background processes start. A background process is
a block of executable code designed to perform a specific task. Figure 1-6 shows the relationship
between the background processes, the database, and the Oracle SGA. In contrast to a
foreground process, such as a SQL*Plus session or a web browser, a background process
works behind the scenes.
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