1> latest entry of the db2diag.log to a flat file.1
2> latest entry of the db2.nfy to the same file.1
3> cpu usage by the db2 processes to the file.
4> Tablespace usage incase u are using DMS TS.
5> check the disk space usage by the db2 home and write that to file.1
Check the file.1 periodically and you will be able to know the latest status of the server. We have implemented the above in our project and have found it is very helpful in monitoring the server.