n is either 1 (true) or 0 (false). The default value is 0.
When OldZU5 is enabled (n = 1), switching to the current namespace using the ZN command clears the global vector cache. When this parameter is not enabled, switching to the current namespace has no effect.
Changing This Parameter
On the Compatibility page of the Management Portal (System Administration > Configuration > Additional Settings > Compatibility), in the OldZU5 row, click Edit. Select OldZU5 to enable this setting.
Instead of using the Management Portal, you can change OldZU5 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).