Active Session History (ASH) performed an emergency flush

ARC1: STARTING ARCH PROCESSES COMPLETE
ARC2: Becoming the heartbeat ARCH
Sun Jun ** 10:46:08 ****

Active Session History (ASH) performed an emergency flush. This may mean that ASH is undersized. If emergency flushes are a recurring issue, you may consider increasing ASH size by setting the value of _ASH_SIZE to a sufficiently large value. Currently, ASH size is 134217728 bytes. Both ASH size and the total number of emergency flushes since instance startup can be monitored by running the following query:
select total_size,awr_flush_emergency_count from v$ash_info;



SQL> select total_size/1024/1024,awr_flush_emergency_count from v$ash_info;

TOTAL_SIZE/1024/1024 AWR_FLUSH_EMERGENCY_COUNT
-------------------- -------------------------
                 128                         1


This is not a dynamic paramter :

sql > alter system set "_ash_size"=200M scope=spfile;

SQL> select total_size/1024/1024,awr_flush_emergency_count from v$ash_info;

TOTAL_SIZE/1024/1024 AWR_FLUSH_EMERGENCY_COUNT
-------------------- -------------------------
                 128                         1


Note : This will require a DB restart to take the above changes effective.