Property | Description |
---|---|
Parameter type | Big integer |
Syntax | PGA_AGGREGATE_TARGET = integer [K | M | G] |
Default value | 10 MB or 20% of the size of the SGA, whichever is greater |
Modifiable | ALTER SYSTEM |
Range of values | Minimum: 10 MB
Maximum: 4096 GB - 1 |
Basic | Yes |
PGA_AGGREGATE_TARGET
specifies the target aggregate PGA memory available to all server processes attached to the instance.
Setting PGA_AGGREGATE_TARGET
to a nonzero value has the effect of automatically setting the WORKAREA_SIZE_POLICY
parameter to AUTO
. This means that SQL working areas used by memory-intensive SQL operators (such as sort, group-by, hash-join, bitmap merge, and bitmap create) will be automatically sized. A nonzero value for this parameter is the default since, unless you specify otherwise, Oracle sets it to 20% of the SGA or 10 MB, whichever is greater.
Setting PGA_AGGREGATE_TARGET
to 0 automatically sets the WORKAREA_SIZE_POLICY
parameter to MANUAL
. This means that SQL workareas are sized using the *_AREA_SIZE
parameters.
Oracle attempts to keep the amount of private memory below the target specified by this parameter by adapting the size of the work areas to private memory. When increasing the value of this parameter, you indirectly increase the memory allotted to work areas. Consequently, more memory-intensive operations are able to run fully in memory and less will work their way over to disk.
When setting this parameter, you should examine the total memory on your system that is available to the Oracle instance and subtract the SGA. You can assign the remaining memory to PGA_AGGREGATE_TARGET
.
See Also:
Oracle Database Performance Tuning Guide for more information about setting and tuning thePGA_AGGREGATE_TARGET
parameter