CORBA 2.6.1 Programmer's Guide for C++

Table Of Contents

Chapter 7. Managing Transactions

Components of Transaction Service Implementation

Use of TMF

Transaction Service Features Not Supported in NonStop CORBA

TransactionalObject Interface

Checked Transaction Behavior

Transaction Branches and the Diamond Access Problem

This section describes the NonStop CORBA implementation of the Transaction Service (formerly known as the Object Transaction

Service, or OTS) and explains programming considerations for transactions in NonStop CORBA applications.

The Transaction Service components of NonStop CORBA for C++ applications are referred to collectively as NSOTS. Together, they implement

the

CosTransactions module of the Transaction Service to provide distributed transactional execution.

The OTS_Bank sample is a set of programs that illustrate the use of NSOTS. The Readme file for this sample provides a description and

walkthrough of these programs, including how to build and run them.

Components of Transaction Service Implementation

NSOTS consists of the following components:

OTS, a special client stub that implements the OMG Transaction Service API

NSotsTM, a process that collaborates with the Transaction Management Facility (TMF) on the NonStop system to manage transactions

and that can run as a TS/MP server pool

NSotsXID, a singleton process used to broker transaction identifiers (XIDs) when NSotsTM runs as a TS/MP server pool with multiple

processes

Use of TMF

NSOTS uses the NonStop Transaction Management Facility, or TMF, for transaction management. NSOTS serves in both superior and

subordinate roles to TMF.

NSOTS and TMF communicate through a pseudo-file called a recoverable resource manager (RM) file. They exchange signals through this file

using the TMF APIs. These signals are used to start and terminate transactions. The RM file is also used during the initialization of NSOTS to

recover any in-doubt transactions following a failure.

The operations

tmf_start and tmf_end are added to the CosTransactions::Current interface to control the participation of NSOTS in

outstanding TMF transactions.

When an exception is initiated by TMF, NSOTS assigns the TMF error code to the CORBA exception minor code.

Transaction Service Features Not Supported in NonStop CORBA

The following features of the Transaction Service are not supported by NSOTS:

Nested transactions

TransactionFactory interface (you should design applications to use the CosTransactions::Current interface)

Explicit propagation of transactions

TransactionalObject Interface

An application-defined interface that inherits from the TransactionalObject interface indicates that any transactional context associated with the

client thread should be associated with operations on the object's interface.

Note:

In the OMG Transaction Service version 1.2, use of the

TransactionalObject interface is deprecated in favor of POA

policies.

Checked Transaction Behavior

In performing checked execution for transactions, NSOTS attempts to enforce the rule that only one thread may remain active in a transaction