Temporal circular buffer values must satisfy the constraints specified in the section called “Validity of Temporal Types” so that they are well defined. An error is raised whenever one of these constraints are not satisfied. Examples of incorrect values are as follows.

-- Null values are not allowed
SELECT tcbuffer 'NULL@2001-01-01 08:05:00';
SELECT tcbuffer 'Point(0 0)@NULL';
-- Base type is not a circular buffer
SELECT tcbuffer 'Point(0 0)@2001-01-01 08:05:00';