The Management Database (MGMTDB), or say Grid Infrastructure Management Repository (GIMR) is a database which collects real time performance data of each node.
It can be located at any node but only one instance in the cluster, you may regard it as a RAC one node database. Whenever the hosting node is under some kind of pressure, we can move it to another node.
In this case, the database is originally in the second node.
[grid@primary01 ~]$ crsctl status res ora.mgmtdb
NAME=ora.mgmtdb
TYPE=ora.mgmtdb.type
TARGET=ONLINE
STATE=ONLINE on primary02
[grid@primary01 ~]$ srvctl status mgmtdb
Database is enabled
Instance -MGMTDB is running on node primary02
OK, the instance name (ORACLE_SID) is -MGMTDB. To move it to another node, we can use the following command to relocate it by the user grid.
[grid@primary01 ~]$ srvctl relocate mgmtdb -n primary01
Let's check the result.
[grid@primary01 ~]$ crsctl status res ora.mgmtdb
NAME=ora.mgmtdb
TYPE=ora.mgmtdb.type
TARGET=ONLINE
STATE=ONLINE on primary01
We have moved it to the node 1.
Please note that, MGMTDB takes about 1GB memory of the server, if your RAC servers are small-to-medium scale and tight for resource, you don't have to create it during grid installation. Because you pay more than you get.
If you already have it and feel uncomfortable about it, you may also consider to remove MGMTDB completely.