DBA_HIST_PROCESS_MEM_SUMMARY displays historical information about dynamic PGA memory usage by named component categories for each process.
| Column | Datatype | NULL | Description | 
|---|---|---|---|
| SNAP_ID | NUMBER | NOT NULL | Unique snapshot ID | 
| DBID | NUMBER | NOT NULL | Database ID for the snapshot | 
| INSTANCE_NUMBER | NUMBER | NOT NULL | Instance number for the snapshot | 
| CATEGORY | VARCHAR2(15) | NOT NULL | Category name. Categories include "SQL", "PL/SQL", "OLAP" and "JAVA". Special categories are "Freeable" and "Other". Freeable memory has been allocated to the process by the operating system, but has not been allocated to a category. "Other" memory has been allocated to a category, but not to one of the named categories | 
| NUM_PROCESSES | NUMBER | Number of processes | |
| NON_ZERO_ALLOCS | NUMBER | Number of processes with non-zero allocations | |
| USED_TOTAL | NUMBER | Bytes of PGA memory used by the process for the category | |
| ALLOCATED_TOTAL | NUMBER | Total number of bytes of PGA memory allocated by the process for the category. | |
| ALLOCATED_AVG | NUMBER | Average number of bytes of PGA memory allocated by the process for the category | |
| ALLOCATED_STDDEV | NUMBER | Standard deviation of the number of bytes of PGA memory allocated by the process for the category | |
| ALLOCATED_MAX | NUMBER | Maximum bytes of PGA memory ever allocated by the process for the category | |
| MAX_ALLOCATED_MAX | NUMBER | Maximum bytes of PGA memory that can be allocated by the process for the category |