TMF Introduction (G06.26+)

Transaction Coordination

HP NonStop TMF Introduction—522414-002

2-3

Resource Managers and Transaction Gateways

In general, a resource manager is a software entity that manages a certain part of a

computer system’s shared resources. Many other software entities can request

access to these resources from time to time, using services that the resource manager

provides. This general concept of a resource manager is treated extensively in the

literature of the Open Group, a vendor and technology-neutral industrial consortium

dedicated to enterprise interoperability.

When the shared resources are persistent, such as a database that contains

information on disk, the resources of a transaction manager are used to maintain the

consistency of that data across updates.

With respect to distributed transaction processing, a resource manager is a collection

of routines that enables cooperation between different transaction management

systems running on different platforms. A resource manager manages transaction

objects and provides services to applications or other resource managers. For

example, a resource manager may be a database system, such as NonStop SQL, or a

transaction queue manager.

Resource managers are run by a process known as a transaction gateway. The

gateway provides communication between the local and remote transaction managers.

This capability, in turn, enables communication between different processing

environments—for example, between TMF running on a NonStop server and a foreign

transaction manager running on another platform. The gateway executes the resource

manager routines to support this communication. (In fact, the gateway itself is

regarded as a communication resource manager (CRM) in Open Group terminology.)

The gateway handles all communications between the local and remote nodes

regarding transactions. In particular, the local transaction manager communicates with

a remote node through the gateway. The local transaction manager (TMF on a

NonStop system) treats the gateway as a surrogate resource manager; it does not

directly communicate with any remote resource manager. In the remote node, the

gateway notifies the remote transaction manager that it has a subordinate relationship

to the originating transaction manager. Through the gateway, the local and remote

transaction managers cooperatively participate in an agreement protocol to determine

the outcome of individual transactions.

Note. For more information about heterogeneous transaction processing and resource

managers in general, see the Open Group Transaction Processing Publications, which can be

ordered through many bookstores and from the following Web location:

http://www.opengroup.org/pubs/catalog/tp.htm