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 ASHSIZE to a sufficiently large value. Currently, ASH size is 67108864 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;


MOS: Active Session History (ASH) Performed An Emergency Flush Messages In The Alert Log (Doc ID 1385872.1)

bash-3.2$ sqlplus "/ as sysdba";

SQL*Plus: Release 11.2.0.3.0 Production on Thu Sep 11 14:03:36 2014

Copyright (c) 1982, 2011, Oracle. All rights reserved.
 Connected to:
 Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
 With the Partitioning, OLAP, Data Mining and Real Application Testing options

SQL> select name,open_mode from v$database;

NAME OPEN_MODE
 --------- --------------------
 ANARDB READ WRITE

SQL>

SQL> alter system set "_ash_size" =16777216 scope=spfile;

System altered.

SQL> shut immediate;
 Database closed.
 Database dismounted.
 ORACLE instance shut down.
 SQL> startup;
 ORACLE instance started.

Total System Global Area 1.2831E+10 bytes
 Fixed Size 2171296 bytes
 Variable Size 2080382560 bytes
 Database Buffers 1.0704E+10 bytes
 Redo Buffers 44785664 bytes
 Database mounted.
 Database opened.
 SQL>
 SQL>
 SQL> select name,open_mode from v$database;

NAME OPEN_MODE
 --------- --------------------
 ANARDB READ WRITE

SQL>
 SQL>
 SQL> alter system switch logfile;

System altered.

SQL> /

System altered.

SQL> /

System altered.

SQL> exit

 

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