In a v12.1.1 test system, I just tried to import an XML file containing a different version of the UC_CUSTOM_ATTRIBUTES VARA object, exported from a v12.0.4 system. Immediately, twenty-five errors appeared in the messages window:
3/27/2018 7:34:23 AM - U00015006 System forced memory trace dump.
3/27/2018 9:34:23 AM - U00015006 System forced memory trace dump.
3/27/2018 7:34:23 AM - U00015006 System forced memory trace dump.
3/27/2018 7:34:23 AM - U00015006 System forced memory trace dump.
3/27/2018 9:34:23 AM - U00015006 System forced memory trace dump.
3/27/2018 7:34:23 AM - U00015006 System forced memory trace dump.
3/27/2018 7:34:23 AM - U00015006 System forced memory trace dump.
3/27/2018 9:34:23 AM - U00015006 System forced memory trace dump.
3/27/2018 9:34:23 AM - U00015006 System forced memory trace dump.
3/27/2018 9:34:23 AM - U00015006 System forced memory trace dump.
...
No error appeared in the JUI, and the VARA object was
not replaced. The JUI’s activity indicator was animating for about a minute. After 3 minutes, I tried again and this time the object was successfully replaced.
Note the incorrect time (off by two hours) in half of the messages. The time 7:34 corresponds to UTC/GMT, and 9:34 is local CEST time. The system clocks on both nodes are identical and correct.
Update: I went ahead and opened an incident about this.