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Oracle® Database Heterogeneous Connectivity Administrator's Guide
10g Release 1 (10.1)

Part Number B10764-01
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Performance Tips

This chapter explains how to optimize distributed SQL statements, how to use partition views with Oracle Transparent Gateways, and how to optimize the performance of distributed queries.

This chapter includes the following sections:

Optimizing Heterogeneous Distributed SQL Statements

When a SQL statement accesses data from non-Oracle systems, it is said to be a heterogeneous distributed SQL statement. To optimize heterogeneous distributed SQL statements, follow the same guidelines as for optimizing distributed SQL statements that access Oracle databases only. However, you must consider that the non-Oracle system usually does not support all the functions and operators that Oracle supports.

The Oracle Transparent Gateways tell Oracle (at connect time) which functions and operators they do support. If the non-Oracle data source does not support a function or operator, then Oracle performs that function or operator. In this case, Oracle obtains the data from the other data source and applies the function or operator locally. This affects the way in which the SQL statements are decomposed and can affect performance, especially if Oracle is not on the same machine as the other data source.

Optimizing Performance of Distributed Queries

You can improve performance of distributed queries in several ways. These are: