Cluster Health Monitory process CHM (ORA.CRF)- 11g onwards

Oracle 12c MGMTDB Database and 11g Berkley database

MGMTDB is a new oracle 12c database instance which is used for storing Cluster Health Monitor (CHM) data.
In 11g this was being stored in Berkley database ( .bdb files).
During Oracle Grid infrastructure 12.1.0.1 installation, there is an option to configure (Or Not) Grid Infrastructure Management Repository . If you choose YES, then you will see instance -MGMTDB running on ONE OF THE NODES on your cluster.

You can identify the current master using below command
$ oclumon manage -get MASTER
MGMTDB DB instance can be managed using srvctl commands
ex:     $ srvctl status mgmtdb
          $ srvctl config mgmtdb 

Cluster Health Monitor resource and daemons.
ora.crf resource was introduced Starting Oracle 11gR2 version.
ora.crf is the Cluster Health Monitor resource name. It collects OS statistics (system metrics) in real time, such as memory and swap space usage, processes, IO usage, and network related data.
osysmond is the monitoring and OS metric collection daemon that sends the data to ologgerd.
ologgerd receives the information from all the nodes and persists in a Berkeley DB based database.

In Oracle 12.1.0.1 – GIMR is optional. Whereas in Oracle 12.1.0.2 – it’s mandatory  and it’s not supported to be turned off with the exception of Exadata.
I’ve searched a lot to find out why it is not supported to be turned off, but I still do not have that answer. I only know that TFA collects some information from MGMTDB and if we turn it off, it means TFA will not be able to retrieve that information. In 19c GIMR is optional again.

The reason why I want to turn it off, is that there are several bugs related to MGMTDB. We have noticed that several customers had performance related issues because of MGMTDB. The repository database was able to use almost 100% of CPU resources. In addition to this, one customer noticed that MGMTDB increased up to 60GB and exhausted GRID diskgroup where OCR and voting files were located (this size is not normal for 3-node cluster).

So If for some reasons you decided to turn off the MGMTDB database on your cluster, you have to make sure to stop and disable “ora.crf” resource.

     $ crsctl stop resource ora.crf -init       $crsctl modify res ora.crf -attr ENABLED=0 -init
     ps -ef | grep osysmond
     ps -ef | grep ologgerd