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<title>Berkeley DB Reference Guide: What other services does Berkeley DB provide?</title>
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<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Introduction</dl></h3></td>
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<h1 align=center>What other services does Berkeley DB provide?</h1>
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<p>Berkeley DB also provides core database services to developers. These
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<p><dt>Page cache management:<dd>The page cache provides fast access to a cache of database pages,
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handling the I/O associated with the cache to ensure that dirty pages
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are written back to the file system and that new pages are allocated on
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demand. Applications may use the Berkeley DB shared memory buffer manager to
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serve their own files and pages.
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<p><dt>Transactions and logging:<dd>The transaction and logging systems provide recoverability and atomicity
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for multiple database operations. The transaction system uses two-phase
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locking and write-ahead logging protocols to ensure that database
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operations may be undone or redone in the case of application or system
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failure. Applications may use Berkeley DB transaction and logging subsystems
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to protect their own data structures and operations from application or
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<p><dt>Locking:<dd>The locking system provides multiple reader or single writer access to
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objects. The Berkeley DB access methods use the locking system to acquire
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the right to read or write database pages. Applications may use the
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Berkeley DB locking subsystem to support their own locking needs.
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<p>By combining the page cache, transaction, locking, and logging systems,
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Berkeley DB provides the same services found in much larger, more complex and
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more expensive database systems. Berkeley DB supports multiple simultaneous
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readers and writers and guarantees that all changes are recoverable, even
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in the case of a catastrophic hardware failure during a database update.
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<p>Developers may select some or all of the core database services for any
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access method or database. Therefore, it is possible to choose the
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appropriate storage structure and the right degrees of concurrency and
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recoverability for any application. In addition, some of the subsystems
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(for example, the Locking subsystem) can be called separately from the
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Berkeley DB access method. As a result, developers can integrate non-database
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objects into their transactional applications using Berkeley DB.
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