n is either 1 (true) or 0 (false). The default value is 0.
When NullSubscripts is enabled (n = 1), null subscripts are allowed on global references. When this parameter is not enabled, a null subscript causes a <SUBSCRIPT> error. InterSystems recommends leaving this setting disabled.
Changing This Parameter
On the Compatibility page of the Management Portal (System Administration > Configuration > Additional Settings > Compatibility), in the NullSubscripts row, click Edit. Select NullSubscripts to enable this setting.
Instead of using the Management Portal, you can change NullSubscripts in the Config.Miscellanous class (as described in the class reference) or by editing the CPF in a text editor (as described in the Editing the Active CPF section of the “Introduction to the Configuration Parameter File” chapter in this book).