What does the ORA-21779 mean?

Hi,

I would like to know what the ORA-21779 -  Duration Not Active means, why it can occurre, what can be done
to resolve it, what is the duration that has been terminated and why has it been terminated.

The description below doesn't include useful information:

Cause: User is trying to use a duration that has been terminated.
Action: User should avoid performing such operation.

Thanks in advance,

Rehab