RAM memory monitoring is implemented in Oracle by enhancing the v$process view.
The new columns in the v$process view allow you to show details about the (PGA) program global area regions for all current Oracle processes.
The PGA is a dedicated area of RAM memory used by individual processes to perform RAM intensive functions, such as sorting.
The three new columns in the v$process view include
After analyzing these metrics, you can
see the actual RAM utilization for individual background processes within the Oracle environment and
also look at the RAM demands of individual connections to the database.
To illustrate, consider the following query:
col c1 heading 'Program|Name' format a30
col c2 heading 'PGA|Used|Memory' format 999,999,999
col c3 heading 'PGA|Allocated|Memory' format 999,999,999
col c4 heading 'PGA|Maximum|Memory' format 999,999,999
This example provides insight into the behavior of the Oracle database engine. One can see that the (LGWR) log writer process is the highest consumer of PGA RAM memory, which makes sense because the
Oracle Log Writer process must transfer redo log images from the Log Buffer (in RAM memory) to the online redo log filesystem. You can also see high RAM memory utilization for the (DBW0) Database Writer process.
The asynchronous I/O processes used by Oracle make extensive use of RAM memory resources to ensure that all database changes are successfully written to the database.