Martin, The "kfk: async disk IO" seems to be linked to the io_submit system call. You could check your number of async io processes. But don't look at the number of occurrences to determine how "heavy" an event is, look at the time spend. There is no relation between number of occurrences and time spend. Regards, Freek D'Hooge Uptime Oracle Database Administrator email: freek.dhooge@xxxxxxxxx tel +32(0)3 451 23 82 http://www.uptime.be disclaimer: www.uptime.be/disclaimer -- From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On Behalf Of Martin Berger Sent: dinsdag 7 december 2010 9:50 To: Oracle-L Freelists Subject: what is "kfk: async disk IO"? Hi, can anyone please hint me to some information about kfk: async disk IO ? A little query on v$sessions gave me USERNAME EVENT COUNT(*) ------------------------------ -------------------------------------------------- ---------- APPS ges message buffer allocation 98 APPS CSS operation: action 2 APPS Streams AQ: waiting for messages in the queue 9 SYS SQL*Net message to client 1 APPS SQL*Net message from client 147 APPS kfk: async disk IO 1646 as kfk: async disk IO is the bigest contributor, I'd like to investigate a little bit. for the records: 11.2.0.1 - 2 node RAC - RedHat 5.4 Linux 64-bit. (yes, it's EBS - but don't ask me the exact pach level, please - I assume 11.5.10???) thnx Martin -- //www.freelists.org/webpage/oracle-l