tempspace usage

Is there a way to determine (or trace) which individual statements are causing tempspace to be allocated to a session? I've got a databases where half a dozen sessions seem to gradually allocate more and more tempspace (as measured by v$sort_usage), and then never release it.=20 Eventually they acquire almost all of the available space, which of course causes a flurry of ORA-1652 errors from other sessions.

At the moment, I'm examining a trace from one of these sessions. So far, I don't see anything which could cause this behaviour... a few inserts, some relatively simple selects, nothing particularly complex.  Any suggestions on how to troubleshoot this sort of issue?

The DB in question is Oracle 8.1.7.4.0 (32-bit), running on Solaris 8.

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