Active Session History (ASH) performed a Emergency Flush Messages in the Alert Log

Active Session History (ASH) performed a Emergency Flush Messages in the Alert Log (document ID 1385872.1)

In this Document Symptoms Cause Solution This document was being delivered to your via Oracle support ' s Rapid Visibility (RaV) process and therefore have not been sub Ject to an independent technical review. Applies To: Oracle database-enterprise edition-version 11.1.0.6 and later Information in this document applies to any platform. Symptoms Periodically see the following message in the alert log. Active Session History (ASH) performed an emergency flush. This may mean, ASH is undersized. If Emergency flushes is a recurring issue, you could consider increasing ASH size by setting the value of _ash_size to a su fficiently large value. Currently, ASH size is <some value> bytes. Both ASH size and the total number of emergency flushes since instance startup can is monitored by running the following q Uery:select Total_size,awr_flush_emergency_count from V$ash_info; Cause Typically some activity on system causes more active sessions, therefore filling the ASH buffers faster than usual causing This message is displayed. It is not a problem per se, just indicates the buffers might need to being increased to support peak activity on the database . Solution The current ASH size was displayed in the "message in the" alert log, or can be found using the following SQL statement. Select Total_size from V$ash_info; Then increase the value for _ash_size by some value, like 50% more than what is currently allocated. For example if Total_size = 16MB, then a increase of 50% more would be (16MB + (16MB * 50%)) = 24MB. Sqlplus/as sysdba alter system set "_ash_size" =25165824; You can verify the change using the following select: Select Total_size from V$ash_info;Example:Production Environment Alarm log: Active Session History (ASH) performed an emergency flush. This may mean, ASH is undersized. If Emergency flushes is a recurring issue, you could consider increasing ASH size by setting the value of _ash_size to A sufficiently large value. Currently, ASH size is 16777216 bytes. Both ASH size and the total number of emergency flushes since instance startup can is monitored by running the following q Uery: Select Total_size,awr_flush_emergency_count from V$ash_info; Enquiry and Processing:Sql> Select Total_size/1024/1024,awr_flush_emergency_count from V$ash_info; total_size/1024/1024 Awr_flush_emergency_count --------------------                   ------------------------- 16 1 Sql> alter system set _ash_size "= 25165824; System altered. Sql> select Total_size/1024/1024,awr_flush_emergency_count from V$ash_info; total_size/1024/1024 Awr_flush_emergency_count --------------------              ------------------------- 24 2

Active Session History (ASH) performed a Emergency Flush Messages in the Alert Log