Forte Transaction Management & 2PC

Question

Forte Transaction Management & 2PC
The main purpose of 2PC in a distributed transaction manager is
to enable recovery from a failure that occurs during the window
of transaction commit processing. The Forte transaction manager was built
with this in mind but only with respect to the "volatile" (or "in memory")
objects that Forte manages. What this implies is that because Forte stores
objects in memory and not persistently on disk, the requirement of recovery
for these objects is significantly reduced (if not eliminated all together).
Forte follows a distributed 2PC model in that tasks and messages carry
along with them transaction identification and, during commit processing,
every distributed participant is polled for its availability to commit
the transaction. Applications saving persistent data to disk during a
distributed Forte transaction need to concern themselves with the potential
for failure during the commit processing window. Forte's prepare phase polls
each site (confirming a communications link with each distributed participant)
but no prepare request goes to the database primarily because (in release 1 and
2 of forte) no database supported a general distributed two-phase commit
(one could take issue with that in the case of Sybase, but rather than debate
this point, suffice it to say that the general direction in the industry for
support of this functionality was through TP monitors -- more on that later).
Once all sites are ready to commit Forte expects that the commit will
complete successfully. If at this moment, for example, a participating
Sybase server terminates (with data not yet committed) while a participating
Oracle server has already committed its unit of work, then the outcome of
the distributed transaction is inconsistent - if no one has yet committed
Forte will still abort the transaction. This "window of inconsistency"
is documented in the Forte TOOL manual.
Mission critical applications that require distributed transactions can
address this window of inconsistency in a number of ways:
* Utilize a TP monitor such as Encina (see below)
* Log distributed updates in an auxiliary database table (much like a
distributed transaction monitor's transaction-state log). This approach has
been the traditional banking application solution prior to the commercial
availability of products like Encina, Tuxedo, TopEnd, etc.
This solution is somewhat complex and is usually not generic enough
so as not to have to change code every time a new table or database
site is introduced into the application's data model.
* Rearrange the data model in order to eliminate the need for distributed
transactions. This is usually only a temporary solution (with smaller
numbers of active clients) and cannot be applied to complex legacy systems.
With the advent of the X/Open distributed transaction architecture (the
XA Interface) more database vendors have found that by complying with the
XA interface they can plug their database-specific implementation of
transaction into a globally managed transaction, with commit and abort
processing being conducted by a central coordinator. Of course, the
overall transaction manager coordinating the global transaction must
itself, persistently record the state of the different distributed
branches participating in the transaction. A significant portion of
the functionality provided by products such as Encina, Tuxedo, TopEnd and
OpenTP1 is to provide exactly this global transaction management.
Rather than extend the Forte distributed transaction manager with the
functionality necessary to manage and recover distributed transactions
that modify data on disk, Forte has chosen to integrate with the emerging
set of commercial transaction monitors and managers. This decision was
built into the original design of the Forte transaction model (using XA and
early Tuxedo white-papers as guidelines):
* In Forte release 2 an integration with Encina was delivered.
* In January 1997 a press release announced an integration of
OpenTP1 with Forte for release 3.
* The Forte engineering staff is currently investing integration
with other transaction management products as well.
Neil Goodman,
Forte Development.

Answer 1

You don't. ("manage" a transaction)
There is nothing really to "manage".
A transaction is automatically started when you make any changes to data (e.g. fire off a DML statement).
You simply needs to issue a COMMIT or ROLLBACK when needed. A COMMIT at the end of the business transaction and not before (i.e. no committing every n number of rows). A ROLLBACK when hitting an exception or business logic error that requires the uncommitted changes to be undone.
That in a nutshell is it. It is that simple.
Oracle also supports creating savepoints and rolling back only some changes made thus far in the transaction.
The only other thing to keep in mind that a DDL in Oracle issues an implicit commit. Firing off a DDL with cause any exiting uncommitted transaction to be committed.
Transaction "logic/management" should not be made more complex than this.