Event Monitor (EMON) Slave Process Constantly Consuming CPU (Doc ID 1603844.1)

Event Monitor (EMON) slave process is consuming CPU.

Multiple stacks from the process obtained via 

connect / as sysdba

oradebug setospid 1379

or use  the following to find EMON process

In 11g ps -ef | grep EMON

In 12c ps-ef |grep ennn

oradebug SHORT_STACK

have the form

Oracle pid: 43, Unix process pid: 1379, image: oracle@feltux3154 (E000)

_write()+10<-nttwr()+275<-nsntwrn()+111<-nspsend()+935<-nsdo()+4694<-nsfull_sd()+46<-kpcesend()+952<-kponsnd()+392<-kponepms()+1729<-kponprmsg()+405<-kponemn0()+597<-kponemn()+1152<-ksvrdp()+3653<-opirip()+901<-opidrv()+684<-sou2o()+87<-opimai_real()+280<-ssthrdmain()+295<-main()+203<-_start()+108

which indicates it is stuck in a network write.

CAUSE

The cause of this issue has been identified in unpublished enhancement Bug 9735536.  The emon process is stuck in a network write probably trying to communicate with a client that is not responding and this fix detects this and removes the unreachable client.

SOLUTION

The workaround is to kill the emon slave process via

kill -9 ps_id

where ps_id is the process id of the emon slave.

The emon slave will automatically restart when it is next required to do so.

To permanently resolve the issue if the release is 11.2.0.3 or below apply Patch 9735536 (Just apply the fix, no need to set any underscore parameters to activate)

The fix for 9735536 is first included in 11.2.0.4 and higher.

In 11.2.0.4 onwards do the following to enable the fix for unpublished Bug 9735536 :

connect / as sysdba

alter system set "_client_enable_auto_unregister"=true scope=spfile

shutdown immediate

startup