Distributed Data Warehouses Location Transparency Oracle Tips by Burleson Consulting

The Data Warehouse Development Life Cycle

Distributed Oracle Data Warehouses

Location Transparency

Location transparency refers to the ability of a distributed database to function as a unified whole and appear to end users as if they are accessing a single database. The end users of a distributed warehouse most likely do not care where data resides or what access method the database invokes to service their queries. Location transparency is rather complex, and it becomes even more complex when we are dealing with distributed transactions among different relational databases. While many third-party vendors have achieved this type of transparency, it is not without cost. Even a distributed system composed entirely of relational databases still has to deal with variances in each database's "100% ANSI compliant" SQL. As we see in figure 9.5, the tools must translate the dialects from each database vendors SQL.

Figure 9.5 Relational architectural distribution.

One of the most pressing problems with distributed databases is managing the various dialects of SQL. Every major database vendor adds features and extensions to the standard SQL, ostensibly to improve their implementation of SQL. Consequently, any queries that use special features may fail in a distributed multivendor architecture.

SQL dialect problems are even more aggravating when the distributed database is composed of databases from non-relational architectures. Sophisticated techniques must be used to interrogate a distributed query to identify which data components reside in which architectures. Then, sub-queries must be decomposed into appropriate access languages (see Figure 9.6).

Figure 9.6 Multiple database architecture database queries.

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This is an excerpt from "High Performance Data Warehousing", copyright 1997.

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