If a parameter is classified as master, you only need to set it at the Greenplum master instance. If it is also a session parameter, you have the additional flexibility of setting the parameter for a particular database, role or session. If a parameter is set at multiple levels, then the more granular level takes precedence. For example, session overrides role, role overrides database, and database overrides system.

Setting Parameters at the System Level

Setting master parameters in the master postgresql.conf file makes that setting the new system-wide default.

1.Edit the $MASTER_DATA_DIRECTORY/postgresql.conf file.

2.Find the parameter you want to change, uncomment it (remove the preceding # character), and set it to the desired value.

3.Save and close the file.

4.For session parameters that do not require a server restart, you can upload the postgresql.conf changes as follows:
$ gpstop -u

5.For parameter changes that require a server restart, restart Greenplum Database as follows:
$ gpstop -r