In the database settings, I saw the lines:

_client_enable_auto_unregister = TRUE _undo_autotune = FALSE

It is clear that the underscore before the parameter indicates that these parameters are not documented and are not recommended for use on their own. But what do they do? About _undo_autotune found that he is responsible for enable auto tuning of undo_retention , but did not understand what is meant by this.

1 answer 1

The hidden parameter _client_enable_auto_unregister used to "cure" Bug 9735536 in Oracle 11.2.0.4 and later (see SOLUTION below).

Description of the "bug":

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:

It is not clear that it has reached a level of 9735536 enhancement.

SOLUTION:

Ear slave process via

kill -9 ps_id

where ps_id is the process id of the emon slave.

It will automatically restart it.

If you are a pre-11.2.0.3, apply Patch 9735536

In 11.2.0.4 onwards Bug 9735536 for the fix for unpublished:

 connect / as sysdba alter system set "_client_enable_auto_unregister"=true scope=spfile shutdown immediate startup