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The Transaction Manager
Managing Transactions
In an X/Open DTP environment, a single transaction can span one or several
RMs. The TM can manage both types of transactions, local (one RM) and
global (several RMs). For a general description of local and global
transactions, see page 1-7.
Local Transactions
A local transaction involves one service in a single RM. A local transaction can
occur in one of the following ways:
■
Under the control of the TM
The application program uses special transaction-management calls,
provided as part of the AP-TM interface, to begin and commit the
work in the local transaction. For more information, see “The
AP-to-TM Interface” on page 1-24.
■
Under the control of the RM
The application program uses the appropriate calls in the AP-RM, the
native RM API, to start and end the local transaction. When this API
is SQL, the application program starts the transaction with a BEGIN
WORK statement and ends the transaction with a COMMIT WORK
statement, or it uses single-statement transactions (implicit transactions). For more information, see “The AP-to-RM Interface” on
page 1-23.
Global Transactions
In the X/Open DTP environment, many RMs can operate in support of the
same global transaction. For example, an application program can require
updates to several databases in several RMs in a single global transaction. The
commitment of work in one transaction branch can be contingent on transaction branches that occur at other RMs. RMs are typically unaware of the
work that other RMs perform. A global transaction includes more than one RM.
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Informix Embedded SQL TP/XA Programmer’s Manual