eG Monitoring
 

Measures reported by OraRacPgaTest

A PGA is a memory region that contains data and control information for a server process. It is nonshared memory created by Oracle cluster when a server process is started. Access to the PGA is exclusive to the server process. There is one PGA for each server process. Background processes also allocate their own PGAs.

If the PGA runs out of memory, then critical cluster processes may not run. To avoid this, administrators can use the Oracle RAC PGA test to keep an eye on the memory consumption by the PGA and be proactively alerted administrator if one/more server processes are draining memory from the PGA rapidly.

Outputs of the test : One set of results for every node in the cluster

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
Pga_curr_usage Indicates the amount of PGA memory that is currently in use. MB Ideally, the value of this measure should be low. A steady rise in this value is a sign of excessive consumption of PGA memory by server processes.
Pga_hit_pct Indicates the ratio of the total number of bytes processed in the PGA versus the total number of bytes processed plus extra bytes read/written in extra passes. Percent A value of 100% means that all work areas executed by the system since instance startup have used an optimal amount of PGA memory.

If the value of this measure falls below 95%, it indicates that the work area cannot run optimal. As a result, one or more extra passes will be performed over the input data. In this case therefore, you can take one of the following actions:

  • When not using Automatic PGA memory, then increase SORT_AREA_SIZE init parameter.
  • When using Automatic PGA memory, then increase PGA_AGGREGATE_TARGET init parameter.
Pga_usage_pct Indicates the percentage of PGA memory that is consumed by the server processes. Percent Ideally, the value of this measure should be low. If this value rapidly approaches 100%, it indicates that the PGA is about to run out of free memory. You may then want to consider resizing your PGA memory region by increasing the value for the PGA_AGGREGATE_TARGET init parameter.
Exceeded_pga_memory Indicates the amount of memory that was additionally allocated to the PGA after the the PGA had run out of free memory. MB Sometimes, the PGA memory may exceed the allocated PGA memory value by a small percentage and this may last only for a short period of time when the work area workload is increasing very rapidly or when PGA_AGGREGATE_TARGET is set to a small value.

If the value of this measure increases rapidly, then, administrators should consider resizing the PGA memory region by increasing the value for the PGA_AGGREGATE_TARGET parameter.