The route a SQL statement takes during execution
is critical for high performance. Once application developers and DBAs
have tuned a SQL statement for maximum efficiency, they can force the Oracle
optimizer to use the same execution plan regardless of environmental changes.
This provides critical stability and predictability in the face of software upgrades,
schema changes, data-volume changes, and so on. Oracle9i added the capability
for administrators to edit stored outlines.
Since Oracle Database 10g, youcan select better execution plans for the
optimizer to use in conjunction with poorly written SQL to improve OLTP performance
without having to rewrite the SQL. The SQL Tuning Advisor performs
these advanced optimizations on SQL statements, and can then create an
improved SQL Profile for the statement. This profile is used instead of the original
optimization plan at runtime.
Scalability
Both the shared server and the Database Resource Manager help Oracle support
larger or mixed user populations.
Multi-Threaded Server/shared server
Oracle7 introduced the Multi-Threaded Server (MTS, renamed the shared server in
Oracle9i) (described in Chapter 2) to allow Oracle to support larger user populations.
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