Sets a name that identifies this database cluster (instance) for various purposes. The cluster name appears in the process title for all server processes in this cluster. Moreover, it is the default application name for a standby connection (see synchronous_standby_names.)
The name can be any string of less than
NAMEDATALEN characters (64 characters in a standard build). Only printable ASCII characters may be used in the
cluster_name value. Other characters will be replaced with question marks (
?). No name is shown if this parameter is set to the empty string
'' (which is the default). This parameter can only be set at server start.