After upgrading Oracle Grid Infrastructure, upgrade the Enterprise Manager Cloud Control target.
Because Oracle Grid Infrastructure 21c is an out-of-place upgrade of the Oracle
Clusterware home in a new location (the Oracle Grid
Infrastructure for a cluster home, or Grid home), the path for
CRS_HOME parameter in some parameter files
must be changed. If you do not change the parameter, then you
encounter errors such as "cluster target broken" on Oracle
Enterprise Manager Cloud Control.
To resolve the issue, update the Enterprise Manager Cloud Control target, and then update the Enterprise Manager Agent Base Directory on each cluster member node running an agent.