[SQL] Is it possible to "truncate" a LOB?

[Stephen Crawley]

[I asked this question on the "interfaces" list, but nobody answered ...]

Suppose that I have created a LOB, written a bunch of data to it, and 
committed.

Is it now possible to rewrite the LOB to contain a lesser amount of data?
In other words can I do the equivalent of UNIX open(..., O_WRONLY | O_TRUNC) 
or ftruncate(...) on a LOB?

Or am I forced to delete the existing LOB and create a new one if I want
to shrink the size of the stored data?

-- Steve