TMF Operations and Recovery Guide (G06.26+)

Routine Maintenance
HP NonStop TMF Operations and Recovery Guide—522417-003
2-22
Normal Distributed Transaction Processing
When a heterogeneous transaction in your local TMF system requires access to a
table or file in a database managed by a foreign transaction manager, TMF and the
foreign transaction manager cooperate in achieving this access.
The system in which a distributed transaction originates is referred to as the parent
node while the secondary system, whose resources the transaction requires, is
referred to as the child node. Thus, when a node sends a transaction to another node,
the first (sending) node is the parent node, and the second (receiving) node is the child
node. If the second node requires resources from another system, the second node is
now both a child to the first node, and a parent to the third node; a node can have
more than one child node for a given transaction.
Maintaining distributed transactions requires an understanding of their normal
processing states and their dependence on the availability of communication links.
Normal Distributed Transaction Processing
Table 2-5 summarizes the usual progression of states that a homogeneous distributed
transaction goes through in the parent node and in a child node. Note that a
distributed transaction can involve not just one, but several child nodes. In such a
case, the transaction exists simultaneously in the parent node and in all involved child
nodes.
Table 2-5. Homogeneous Distributed Transaction States (page 1 of 2)
Transaction States in the…
Parent Node Child Node Activity
ACTIVE (does not yet
exist)
An application program starts a transaction in the parent
node by executing a BEGINTRANSACTION procedure
call. The transaction requires access to a table, file, or
server process on a child node.
ACTIVE ACTIVE The TMP in the parent node sends a message to the
TMP in the child node, which starts the transaction in the
child node.
ACTIVE PREPARED When the application executes an ENDTRANSACTION
procedure call, the parent-node TMP sends a message
to the child-node TMP, which then changes the state of
the transaction from active to prepared.