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87 lines
4.4 KiB
HTML
<!--$Id: env_set_shm_key.so,v 10.5 2000/08/09 15:45:52 sue Exp $-->
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<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.-->
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<!--All rights reserved.-->
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<html>
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<head>
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<title>Berkeley DB: DBENV->set_shm_key</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++">
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</head>
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<body bgcolor=white>
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<a name="2"><!--meow--></a>
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<table><tr valign=top>
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<td>
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<h1>DBENV->set_shm_key</h1>
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</td>
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<td width="1%">
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<a href="../api_c/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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<hr size=1 noshade>
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<tt>
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<h3><pre>
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#include <db.h>
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<p>
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int
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DBENV->set_shm_key(DB_ENV *dbenv, long shm_key);
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</pre></h3>
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<h1>Description</h1>
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<p>Specify a base segment ID for Berkeley DB environment shared memory regions
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created in system memory on VxWorks or systems supporting X/Open-style
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shared memory interfaces, e.g., UNIX systems supporting
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<b>shmget</b>(2) and related System V IPC interfaces.
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<p>This base segment ID will be used when Berkeley DB shared memory regions are
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first created. It will be incremented a small integer value each time
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a new shared memory region is created, that is, if the base ID is 35,
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the first shared memory region created will have a segment ID of 35 and
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the next one a segment ID between 36 and 40 or so. A Berkeley DB environment
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always creates a master shared memory region, plus an additional shared
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memory region for each of the subsystems supported by the environment
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(locking, logging, memory pool and transaction), plus an additional
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shared memory region for each additional memory pool cache that is
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supported. Already existing regions with the same segment IDs will be
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removed. See <a href="../ref/env/region.html">Shared Memory Regions</a>
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for more information.
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<p>The intent behind this interface is two-fold: without it, applications
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have no way to ensure that two Berkeley DB applications don't attempt to use
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the same segment IDs when creating different Berkeley DB environments. In
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addition, by using the same segment IDs each time the environment is
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created, previously created segments will be removed, and the set of
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segments on the system will not grow without bound.
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<p>The DBENV->set_shm_key interface may only be used to configure Berkeley DB before
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the <a href="../api_c/env_open.html">DBENV->open</a> interface is called.
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<p>The DBENV->set_shm_key function returns a non-zero error value on failure and 0 on success.
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<p>The database environment's base segment ID may also be set using the environment's
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<b>DB_CONFIG</b> file. The syntax of the entry in that file is a
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single line with the string "set_shm_key", one or more whitespace characters,
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and the ID. Because the <b>DB_CONFIG</b> file is read when the database
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environment is opened, it will silently overrule configuration done
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before that time.
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<h1>Errors</h1>
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<p><dl compact>
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<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
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<p>Called after <a href="../api_c/env_open.html">DBENV->open</a> was called.
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</dl>
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<h1>See Also</h1>
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<a href="../api_c/env_close.html">DBENV->close</a>,
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<a href="../api_c/env_create.html">db_env_create</a>,
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<a href="../api_c/env_open.html">DBENV->open</a>,
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<a href="../api_c/env_remove.html">DBENV->remove</a>,
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<a href="../api_c/db_err.html">DBENV->err</a>,
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<a href="../api_c/env_strerror.html">db_strerror</a>,
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<a href="../api_c/env_version.html">db_version</a>,
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<a href="../api_c/env_set_cachesize.html">DBENV->set_cachesize</a>,
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<a href="../api_c/env_set_errcall.html">DBENV->set_errcall</a>,
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<a href="../api_c/env_set_errfile.html">DBENV->set_errfile</a>,
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<a href="../api_c/env_set_errpfx.html">DBENV->set_errpfx</a>,
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<a href="../api_c/env_set_flags.html">DBENV->set_flags</a>,
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<a href="../api_c/env_set_mutexlocks.html">DBENV->set_mutexlocks</a>,
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<a href="../api_c/env_set_paniccall.html">DBENV->set_paniccall</a>,
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and
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<a href="../api_c/env_set_verbose.html">DBENV->set_verbose</a>.
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</tt>
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<table><tr><td><br></td><td width="1%">
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<a href="../api_c/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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