Each memory summary table has these summary columns containing aggregated values: 

• COUNT_ALLOC , COUNT_FREE 

The aggregated numbers of calls to memory-allocation and memory-free functions. 

• SUM_NUMBER_OF_BYTES_ALLOC , SUM_NUMBER_OF_BYTES_FREE 

The aggregated sizes of allocated and freed memory blocks. 

• CURRENT_COUNT_USED 

The aggregated number of currently allocated blocks that have not been freed yet. This is a convenience column, equal to COUNT_ALLOC − COUNT_FREE . 

• CURRENT_NUMBER_OF_BYTES_USED 

The aggregated size of currently allocated memory blocks that have not been freed yet. This is a convenience column, equal to SUM_NUMBER_OF_BYTES_ALLOC − SUM_NUMBER_OF_BYTES_FREE . 

• LOW_COUNT_USED , HIGH_COUNT_USED 

The low and high water marks corresponding to the CURRENT_COUNT_USED  column. 

• LOW_NUMBER_OF_BYTES_USED , HIGH_NUMBER_OF_BYTES_USED 

The low and high water marks corresponding to the CURRENT_NUMBER_OF_BYTES_USED  column. 

The memory summary tables have these indexes: 

• memory_summary_by_account_by_event_name : 

•Primary key on ( USER , HOST , EVENT_NAME ) 

• memory_summary_by_host_by_event_name : 

•Primary key on ( HOST , EVENT_NAME ) 

• memory_summary_by_thread_by_event_name : 

•Primary key on ( THREAD_ID , EVENT_NAME ) 

• memory_summary_by_user_by_event_name : 

•Primary key on ( USER , EVENT_NAME ) 

• memory_summary_global_by_event_name : 

•Primary key on ( EVENT_NAME ) 

TRUNCATE TABLE  is permitted for memory summary tables. It has these effects: 

•In general, truncation resets the baseline for statistics, but does not change the server state. That is, truncating a memory table does not free memory. 

• COUNT_ALLOC  and COUNT_FREE  are reset to a new baseline, by reducing each counter by the same value. 

•Likewise, SUM_NUMBER_OF_BYTES_ALLOC  and SUM_NUMBER_OF_BYTES_FREE  are reset to a new baseline. 

