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<title>Berkeley DB Reference Guide: Introduction</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<table width="100%"><tr valign=top>
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<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Environment</dl></h3></td>
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<h1 align=center>Introduction</h1>
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<p>A Berkeley DB environment is an encapsulation of one or more databases, log
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files, and shared information about the database environment such as
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shared memory buffer cache pages.
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<p>The simplest way to administer a Berkeley DB application environment is to
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create a single <b>home</b> directory that stores the files for the
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applications that will share the environment. The environment home
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directory must be created before any Berkeley DB applications are run. Berkeley DB
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itself never creates the environment home directory. The environment can
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then be identified by the name of that directory.
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<p>An environment may be shared by any number of processes, as well as by
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any number of threads within those processes. It is possible for an
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environment to include resources from other directories on the system,
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and applications often choose to distribute resources to other
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directories or disks for performance or other reasons. However, by
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default, the databases, shared regions (the locking, logging, memory
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pool, and transaction shared memory areas) and log files will be stored
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in a single directory hierarchy.
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<p>It is important to realize that all applications sharing a database
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environment implicitly trust each other. They have access to each
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other's data as it resides in the shared regions, and they will share
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resources such as buffer space and locks. At the same time, any
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applications using the same databases <b>must</b> share an environment
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if consistency is to be maintained between them.
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