Do we need to increase _ASH_SIZE value?

I see on one of the databases (Oracle EE 11.2.0.4.0)  recurring (4-5 times a month) warning:

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 4194304 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;  total_size=4194304; awr_flush_emergency_count= 0.   AVG_FLUSH_COUNT=34