IBM AS/400e, Руководство пользователя

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IBM Licensed Programs: Database Products
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IBM Licensed Programs: Database Products
A lightweight, update-anywhere capability with row conflict detection, designed for the
Microsoft Office environment, lets Microsoft Jet and Microsoft Access desktop database
applications interoperate with corporate applications through database replication with DB2,
Oracle, Microsoft SQL Server, Informix, Sybase, and Sybase SQL Anwhere. Microsoft Jet is
supported for heterogeneous replication only.
DataJoiner also provides a graphical user interface administration tool for defining data
sources and targets. The Replication Administration tool runs on Windows NT and Windows
95, and in DB2 DataJoiner Version 2.1.1, it will be available only in English.
Users and administrators of DB2 DataJoiner can benefit from significant performance
improvements in a variety of scenarios:
• Global SQL Optimizer with Global Query Rewrite Capability: Major enhancements
to the Global SQL optimizer strengthen DB2 DataJoiner's leadership position in global
query optimization for traditional applications. This new global optimization technology
provides the function and performance needed by customers to analyze and exploit
vast amounts of valuable information stored in their multi-vendor databases.
The increasing importance of decision support applications represents an important
customer trend that can result in very complex, multi-vendor database queries. These
global queries can be written by end users, generated by automatic tools, or produced as
a result of many point-and-click application interfaces popular in today's DOS, Windows,
OS/2, and UNIX environments. The optimizer incorporates a very sophisticated query
rewrite phase that automatically transforms a complex query into a simpler query that
matches the capabilities of the data source.
The global optimizer also looks at a great number of alternatives in its search for the best
query execution plan while employing sophisticated cost modeling techniques.
There are two key steps for improving query performance:
– Pushdown Analysis: The major task of this DB2 DataJoiner function is to make a
recommendation to the DataJoiner optimizer about whether an operation can be
remotely evaluated. It is just a recommendation because the DataJoiner Optimizer
may choose not to perform an operation directly on a remote data source because it is
less cost effective. This recommendation is based on the capabilities known to
DataJoiner about this data source, which may include data types, supported
functions, the data source specifics known to DataJoiner, and additional server
options that a user may have created.
– Remote SQL Generation: The final plan selected by the DataJoiner global optimizer
might consist of a set of steps that can operate on the remote data source. For those
operations that are to be performed by each data source, Remote SQL Generation is
called to generate an efficient SQL statement based on the SQL dialect supported at
the data source.