Resolution:

Shutting down VisiNaming using nsutil command depends on whether Smart Agent is enabled or not.

Smart Agent enabled:

Start VisiNaming with Smart Agent enabled (i.e. the default mode):

> nameserv externalnameservice

Shutdown VisiNaming using the instance's name:

> nsutil shutdown externalnameservice

Smart Agent disabled:

Start VisiNaming with Smart Agent disabled and specify the Naming Context Factory IOR file using "vbroker.naming.factoryIorFile":

> nameserv -J-Dvbroker.agent.enableLocator=false -J-Dvbroker.naming.factoryIorFile=/opt/MicroFocus/VisiBroker/NameServiceIOR/nsfact.ior externalnameservice

Shutdown VisiNaming using the instance's Naming Context Factory stringified IOR :

> nsutil -J-Dvbroker.agent.enableLocator=false shutdown `cat /opt/MicroFocus/VisiBroker/NameServiceIOR/nsfact.ior`

If you prefer to use "file://" URL to specify the Naming Context Factory IOR file for nsutil, then the shutdown command should be :

>nsutil -J-Dvbroker.agent.enableLocator=false shutdown file:///opt/MicroFocus/VisiBroker/NameServiceIOR/nsfact.ior


Please refer to the following documentation for the description of the "vbroker.naming.factoryIorFile" property:
http://supportline.microfocus.com/Documentation/books/VisiBroker/85/wwhelp/wwhimpl/js/html/wwhelp.htm?href=properties.75.1.html#568993

When this property is specified with a value specifying a file name, the Naming Service will store the IOR of context factory in that file. The IOR file can then be used by nsutil utility to shutdown the Naming Service remotely.

Please also refer to the following documentation for nsutil shutdown command usage:
http://supportline.microfocus.com/Documentation/books/VisiBroker/85/wwhelp/wwhimpl/js/html/wwhelp.htm?href=namesrvc.85.1.html#482233

Shuts the VisiNaming Service down gracefully from the command line. The mandatory parameter of this operation specifies either the naming context factory's name as registered with the osagent or the stringified IOR of the factory.