TRANS14 — Subtransactions

Summary: If a subtransaction receives inconsistent replies to
commit_subtransaction (for example a resource throws an exception) then
the specification allows an implementation to either ignore it, or
rollback the subtransaction. Since the subtransaction is possibly now in
an indeterminant state (some resources committed whereas others were
told to rollback) then to guarantee consistency it is advisable to force
the parent transaction to rollback. If this is the case then it may be
useful to inform the application early that any work it may attempt to
do after the subtransaction "commit" (i.e., in the context of the
parent) is going to be undone.