IBM WebSphere Developer Technical Journal: Transactional high availability and deployment considerations in WebSphere Application Server V6

The WebSphere Application Server transaction manager stores
information regarding the state of completing transactions in a persistent form
that is used during transaction recovery. This persistent form is referred to
as the transaction recovery log and is used to complete prepared transactions
following a server failure. This activity is referred to as transaction recovery
In addition to completing outstanding transactions, this processing
also ensures that any locks held in the associated resource managers
are released.

Prior to WebSphere Application Server V6, it was necessary to
restart a failed server to perform recovery processing. Version
6.0 introduces the ability for a peer server (another cluster member)
to process the recovery logs of a failed server while the peer
to manage its own transactional workload. This capability is known as peer recovery processing and supports the resolution of
in-doubt transactions without the need to wait for the
failed server to restart. This facility forms part of the overall WebSphere Application Server high availability (HA) strategy.