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Donald K. Burleson
Oracle Tips |
Number and Placement of
Rollback Segments
Will the Tools Be Linked Single-Task
or Be Independent (Two-Task)?
This question deals with the way the Oracle tools, such as SQLLOADER,
IMP, or EXP, address the Oracle kernel. See Figure 1.1 for a
graphical demonstration of the concept of single-task versus a two-
or multitask structure.
If the tools are linked single-task, they address a specific node’s
Oracle kernel by default. To access another node or another system,
a connect string must be used (connect strings will be covered in
Chapter 14, Managing in a Distributed Environment). This mode is
useful for a single-node database situation and saves on memory and
task usage. This is generally used where a client/server
architecture is not used. It has been demonstrated that relinking
some tools single-task, such as the import and export utilities,
will increase their performance by up to 30 percent.
Tip
Single-task linking will be allowed only in preOracle releases, so
plan now to remove it from use.
If the tools are linked independent, or two-task, a connect string
must always be used. It is called “two-task” because the tools must
run as one task while the Oracle executable runs as another.
Two-task is generally used in a client/server situation. This allows
the following benefits:
Client machines to perform CPU-intensive tasks, offloading these
tasks from the server.*
Movement of tools from one environment to another (such as from a
development area to a production one) without relinking.
* The Oracle8i server to be relinked without relinking all of the
tools.
* Two-task tools can reduce throughput, depending on the machine
they are installed upon. The DBA needs to consider the costs versus
the benefits when deciding whether to use single- or two-task-linked
tools.
This is an
excerpt by Mike Ault’s book “Oracle
Administration & Management”. If you want more current Oracle tips
by Mike Ault, check out his new book “Mike
Ault’s Oracle Internals Monitoring & Tuning Scripts” or
Ault’s Oracle Scripts Download.
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