-I7Berkeley DB Reference Guide: Environment[P1

Berkeley DB Reference Guide: Environment



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Shared Memory Regions



LEach of the Berkeley DB subsystems is described by one or more shared memoryCregions. These regions live in the environment home directory, andHcontain all of the shared information, including mutexes, that describesthe Berkeley DB environment.

OThe Berkeley DB library uses the POSIX mmap (or other similar) interface to mapGthe shared memory regions. Most remote file systems (e.g., the NetworkCFile System (NFS) and the Andrew File System (AFS)), do not supportJmapping files into process memory. For this reason, we strongly recommend>that the database home directory reside in a local filesystem.

DFor remote file systems that do allow system files to be mapped intoFprocess memory, it is important to note that home directories accessedCvia remote file systems cannot be used simultaneously from multipleDclients. None of the commercial remote file systems available today<implement a coherent, distributed shared memory paradigm forIremote-mounted files. As a result, different machines will see differentFversions of these shared regions and the system behavior is undefined.

@Databases, log files and temporary files may be placed on remoteEfilesystems, although the application may incur a performance penalty for doing so.

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