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White Paper:
InterPlex
Enterprise Gateway
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Page 9
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Replicating Updates
Replicating
updates from a DataServer table to the Unisys mainframe can be
accomplished with the use of triggers.
When a trigger fires on the DataServers table, the current user-id
and password is used to log into the Unisys mainframe.
Then the InterPlex enterprise gateway starts up the appropriate
InterPlex SQL generated update sub-program and passes the update statement
for processing. If the update
is successful on the mainframe, then all nodes in the distributed
transaction can be committed. If
the update fails an ensuing rollback will occur.
Another
method that could be adapted to replicate the DataServer’s updates to
the Unisys mainframe would be to establish a Unisys view that contains
information about the updates occurring to the replicated table in the
DataServer database. These
“deferred updates” could be processed against the Unisys database
using application logic to ensure data integrity.
This
same sort of methodology can be applied to “updates” on the Unisys
mainframe database for replication downward to the DataServer database. An application might pull rows of data from the mainframe
based on criteria in date stamp, flags, etc. and then apply the rows to a
local table.
SUMMATION
The
InterPlex Enterprise gateway products will transform your Unisys DMS
database into an accessible data source for use by DataServers such as
Oracle, Enterworks, Information Builder’s EDA Server, etc.
This transformation allows you to use the DataServer’s tools and
development products to create applications without regard to the location
of the data. Location transparency is accomplished with database links and
synonyms.
The
use of various DataServer tools and applications are supported which
allows applications to be developed which can access both the local
DataServer database(s) and Unisys DMS databases.
The integration of the Unisys DMS data source via the InterPlex
Enterprise gateway does not require any changes to be made to applications
at the data source. The
result is that the cooperative server technology is non-intrusive,
providing coexistence and an easy migration path.
InterPlex
Enterprise gateway can be a partner in the two-phase commit transaction
processing. During a
distributed transaction, in which the Unisys is updated, the InterPlex
gateway becomes the commit point site.
That is, the Unisys’ ability to commit or rollback determines the
outcome of the transaction at all participating nodes in the distributed
transaction.
InterPlex
Enterprise gateway and various DataServers provide a single consolidated
view of an organization’s data and services.
A client’s view is that of a single logical database comprising a
distributed database with multiple independent databases, integrated with
services provided by the DataServer’s procedures and functions.
These procedures and functions provide a number of benefits such as
encapsulation of business rules and access to Unisys DMS legacy systems.
The
translation of ANSI SQL to other access methods including Unisys PCIOS files and DMS hierarchical databases is transparent to the user. Data mapping of the data source is an integral part of this
technology, and allows data to be automatically converted and normalized,
if required. The
administration of the Unisys DMS databases and other file structures
remains the responsibility of the existing system administrator.
Also the InterPlex Enterprise gateway product does not override the
security methods native to the Unisys operating environment.
--McConnell
and Associates, Inc.
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UNISYS Integrators