There may be cases where you want to start only the master. This is called maintenance mode. In this mode, you can do things such as connect to a database on the master instance only in utility mode and edit settings in the system catalog, without affecting user data on the segment instances.
To start the master in utility mode
1.Run gpstart using the -m option:
$ gpstart -m
2.Connect to the master in utility mode to do catalog maintenance. For example:
$ PGOPTIONS='-c gp_session_role=utility' psql template1
3.After completing your administrative tasks, you must stop the master in utility mode before you can restart it again in production mode.
$ gpstop -m