MongoDB Enterprise > db.a.insert({}, {writeConcern:{j:true}})
WriteResult({
	"writeError" : {
		"code" : 2,
		"errmsg" : "cannot use 'j' option when a host does not have journaling enabled"
	}
})
MongoDB Enterprise > db.adminCommand("getCmdLineOpts")
{
	"argv" : [
		"./mongod",
		"--storageEngine",
		"inMemory",
		"--journal"
	],
	"parsed" : {
		"storage" : {
			"engine" : "inMemory",
			"journal" : {
				"enabled" : true
			}
		}
	},
	"ok" : 1
}