bigtoyco.com) in SQL queries, inserts, updates, deletions, and other statements.
Oracle Net (previously known as Net8 or SQL*Net in older database releases)
handles the interaction with any network protocols used to communicate with the
remote database transparently.
Although the database link makes data access transparent to users, Oracle still has to
treat interactions over distributed databases differently. Let??™s look briefly at how queries
and updates issued for distributed Oracle databases differ from those issued for a
single Oracle database. When using distributed data in a query, your primary
concern is to properly optimize the retrieval of data for a query. Queries in a single
Oracle database are optimized for performance, most frequently using the cost-based
optimizer, as discussed in Chapter 4. Oracle7 added global cost-based optimization
for the improvement of query performance across distributed databases as well. For
example, the cost-based optimizer considers indexes on remote databases when
choosing a plan, whereas the rule-based optimizer does not.
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