Some databases, like Oracle in particular, don’t seem to allow you to set the maximum duration for transactions (hence locks). This implies that some applications (those that don’t behave well) can be holding long-lived locks on your data. The result is that some data may become unavailable (even for days in one particular case I have seen!!!).
The solution? I am not sure about other products, but the Atomikos transaction libraries make sure that none of your applications can hold locks longer than the configured XA transaction timeout. Meaning: you get the benefit of ensured control and availability of your data. It’s ironic really; many people believe that XA can block your data but as this case shows it is exactly the opposite!