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White Paper:
InterPlex
Enterprise Gateway
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InterPlex Enterprise
Gateway Capabilities
InterPlex
Enterprise gateway is integrated into the DataServer’s environment,
which provides query optimization, transaction coordination for multi-site
transactions, support for different network configurations, and so on.
The DataServer Tools and applications are supported and can be used
to access the Unisys DMS database. 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.
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. Site autonomy is
preserved in the cooperative environment.
For example, administration of the Unisys DMS databases and other
file structures remains the responsibility of the existing system
administrator. Site autonomy
also means that the InterPlex gateway product does not override the
security methods native to the Unisys operating environment.
Location
transparency is accomplished with database links, synonyms, and meta-data.
These objects are created on the DataServers that integrate the
InterPlex transparent gateway into the cooperative server environment.
Implementing Location
Transparency
Location
transparency allows the end-users and programmers of an application to
work without concern as to the physical location of the table data.
Location transparency also simplifies remote data access because
both local and remote access can be hidden from users and objects can be
moved without effecting the current users or applications.
Location
transparency is not automatic, but can be provided using several different
methods available to most DataServers.
These methods include defining a local view that references remote
tables in its definition. A
local synonym or meta-data can hide a database link used to access a
remote table or view and finally, a local stored procedure can access
remote data in the statements in the procedure body.
Users of the stored procedure will simply call it without regard to
where the data resides.
Transparency Using
Synonyms and Meta-Data
Using
a local synonym or meta-data to provide location transparency to the
end-users and applications developers is beneficial because remote data
access is simplified. Remote object identities can be hidden from users,
and objects can be moved with no effect on users or current applications. Data may reside on the Unisys mainframe today but be
“ported” to the DataServer’s database the next.
The users and applications will continue to function with no
effect. Also, using a local
synonym can hide the database link referencing the remote data.
To
summarize, synonyms and meta-data provide both data independence and
location transparency; they permit applications to function without
modification regardless of which database holds the table.
Synonyms and meta-data are used for security and convenience. Creating a synonym or meta-data for an object allows you to
reference the object without specifying the database on which it is
located and provides the capability to use another name for the object.
Transparency Using Views
The Unisys ClearPath IX or 2200 mainframe data
is represented as VIEWS of the DMS, RDMS and PCIOS data structures when
using InterPlex Enterprise gateway products. Most DataServers provide the
ability to define a virtual table or view and save that definition in the
database with a user-defined name.
A
view is considered a virtual table. That
is, it is not physically materialized anywhere until it is needed, when
some SQL statement references it, for instance.
The use of views will allow you to define complex queries once and
use them repeatedly without having to re-invent them. Furthermore, views can be used to enhance the security of
your database while supplying location transparency.
To
summarize, a view is a virtual table that allows you to access data from
other tables and views. A
view contains no data itself, but is constructed at the time an SQL
statement references it. Views
provide an additional level of security by restricting access to a
predetermined set of rows and/or columns.
Views can also hide the complexity of the data, for example,
several tables may be used to construct the results but the user is
unconcerned where the tables reside.
Views allow you to present data from a different perspective by
assigning different column names or using where clauses.
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UNISYS Integrators