TMF Operations and Recovery Guide (G06.26+)

Routine Maintenance
HP NonStop TMF Operations and Recovery Guide—522417-003
2-23
What Happens When a Communication Link Goes
Down
Under normal circumstances, homogeneous distributed transactions are started,
proceed through the various states, and disappear automatically. The TMPs in the
involved systems maintain contact with one another and cooperate in the creation and
management of the various portions of a homogeneous distributed transaction.
Heterogeneous distributed transactions, like homogeneous distributed transactions,
are also started, pass through various states, and disappear automatically. The
transaction managers that handle a heterogeneous distributed transaction cooperate in
its creation, management, and commitment. Details about heterogeneous transaction
processing are complex and involve considerations beyond the scope of this manual.
For further information about heterogeneous transaction processing, see the Open
Group TRANSACTION PROCESSING Publications, available from X/Open
Publications at the following Web location:
http://www.opengroup.org/pubs/catalog/tp.htm
These publications can also be ordered through many bookstores.
What Happens When a Communication Link Goes Down
For homogeneous distributed transactions, as long as the communications links
between network nodes remain available, TMF ensures that the transactions either
commit at all involved nodes or abort at all of them; as a result, the distributed portions
of a database remain consistent with one another. For heterogeneous distributed
transactions, as long as the links between transaction-management subsystems
remain available, TMF and foreign transaction managers cooperate to ensure this
same kind of consistency.
COMMITTED PREPARED After the transaction is in the prepared state in all
involved child nodes, the parent-node TMP changes the
transaction from active to committed and sends a
confirmation message to the child-node TMP.
COMMITTED (no longer
exists)
The child-node TMP commits the prepared transaction,
removes it from the list of transactions in progress, and
sends a confirmation message back to the parent-node
TMP.
(no longer
exists)
(no longer
exists)
After the transaction has been committed in all involved
child nodes, the parent-node TMP removes the
committed transaction from the list of transactions in
progress.
Table 2-5. Homogeneous Distributed Transaction States (page 2 of 2)
Transaction States in the…
Parent Node Child Node Activity