TMF Operations and Recovery Guide (G06.26+)

Routine Maintenance
HP NonStop TMF Operations and Recovery Guide—522417-003
2-21
Maintaining Distributed Transactions
Reason: The available TMP memory in CPU number is
running low.
Meaning. The percentage of extended segment memory allocated by the TMP is at or
above the level that causes TMF to disallow new transactions. New transactions can
start when the memory used decreases to an allowable percentage (see Table 1-4 on
page 1-7 for more information).
Action. Work with the system manager to adjust the TMPMEMTHRESH value for your
system, or change the extended segment size for the TMP.
See Enabling New Transactions on page 3-17 for suggestions on recovering from a
begin-transaction-disable condition. See the TMF Planning and Configuration Guide
for information on configuring the begin-transaction-disable object.
Maintaining Distributed Transactions
TMF can service two kinds of distributed transactions:
•
Homogeneous distributed transactions, where portions of a transaction are
processed by TMF systems on two or more Expand nodes (NonStop systems).
•
Heterogeneous distributed transactions, where portions of a transaction are
processed under the control of multiple transaction managers: TMF and one or
more foreign transaction managers.
For homogeneous distributed transactions, a communication link is managed by the
Expand or FOX subsystem that connects two Expand nodes in a computer network;
when the Expand or FOX subsystem ceases to function, the link goes down.
For heterogeneous distributed transactions, a communication link is the logical
connection of TMF with a gateway process, accomplished through use of a resource
manager. When the gateway process opens the resource manager file, the link comes
up; when the gateway process closes the resource manager file, the link goes down.
(There are three kinds of failure that can cause a link to go down: communication
subsystem failure, gateway process failure, or TMF failure.)
When a homogeneous transaction in your local TMF system requires access to a
table, file, or server on a remote TMF system, the TMP in the local system sends a
message to the TMP in the remote system, which then creates and manages
information about the transaction (in essence, the transaction now exists in two
separate systems, and is managed cooperatively by two different TMPs).
Note. Heterogeneous transactions, and the resource managers that support them, are used in
HP products such as HP NonStop TUXEDO. System managers working with them must
understand many issues involving multiple software subsystems and inter-platform
considerations; complete discussion of heterogeneous transactions lies beyond the scope of
this manual.