In earlier versions of Oracle (release 9i and earlier), RAC required a vendor-supplied clusterware like Sun Cluster or Veritas Cluster Server (except when running on Linux or on Microsoft Windows).
This is also required in a single instance configuration if Automatic Storage Management (ASM) is used.
EVMd spawns a permanent child process called "evmlogger" and generates events.
It will restart automatically on failures and death of the EVMd process does not halt the instance.
OPROCd provides the server fencing solution for the Oracle Clusterware.