Node not connected to NDB

If you in the CMON web interface see "Node not connect to NDB!" there are a couple of things to check:

1. Do you have ndbcluster and ndb_connectstring set in the my.cnf file?
   If not, add the above and restart the mysql server 
2. Are the schema files (.frm files) corrupt? 
   Check the error.log of the mysql server. If it says something with error 157 and entries for various tables you have in NDB then remove the .frm files for the NDB tables. Restart the MySQL Server and it will recreate the .frm files. This problem can be because of an ALTER TABLE and the mysql server never got the new version of the schema files.