instance_name empty in v$instance

 Hello,

We currently have a database (Standard Edition V11.1.0.7) installed by a customer which has a peculiar situation:

SQL> select instance_name from v$instance;

INSTANCE_NAME

--------------------

The instance name field ius empty. I could not find any information in Oracle support or internet on how this field could be empty in the v$instance view. 

The spfile parameter however is filled:

show parameters instance_name

INSTANCE_NAME

--------------------

customerdb1234567

Can anyone explain why this information is lacking in the v$instance view, maybe suggest how to get it into the view?

Many thanks in advance,