PGA Memory Management for Dedicated Mode (102)

You can automatically and globally manage the size of SQL work areas. The database
administrator simply needs to specify the total size dedicated to PGA memory for the
Oracle instance by setting the initialization parameter PGA_AGGREGATE_TARGET. The
specified number (for example, 2G) is a global target for the Oracle instance, and
Oracle tries to ensure that the total amount of PGA memory allocated across all
database server processes never exceeds this target.
With PGA_AGGREGATE_TARGET, sizing of work areas for all dedicated sessions is
automatic and all *_AREA_SIZE parameters are ignored for these sessions. At any
given time, the total amount of PGA memory available to active work areas on the
instance is automatically derived from the parameter PGA_AGGREGATE_TARGET. This
amount is set to the value of PGA_AGGREGATE_TARGET minus the PGA memory
allocated by other components of the system (for example, PGA memory allocated by
sessions). The resulting PGA memory is then allotted to individual active work areas
based on their specific memory requirement.
專有模式下的pga記憶體管理
透過PGA_AGGREGATE_TARGET引數來設定pga可使用的pga記憶體總數
所有的*_AREA_SIZE引數被忽略
對於活動的工作區來說 , 可用的pga記憶體是PGA_AGGREGATE_TARGET指定的值減去pga為其他系統元件分配的記憶體[@more@]