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diff --git a/db/docs/api_cxx/env_open.html b/db/docs/api_cxx/env_open.html new file mode 100644 index 000000000..53c9908dc --- /dev/null +++ b/db/docs/api_cxx/env_open.html @@ -0,0 +1,209 @@ +<!--$Id: env_open.so,v 10.61 2000/12/01 15:50:31 bostic Exp $--> +<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.--> +<!--All rights reserved.--> +<html> +<head> +<title>Berkeley DB: DbEnv::open</title> +<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> +<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++"> +</head> +<body bgcolor=white> + <a name="2"><!--meow--></a> +<table><tr valign=top> +<td> +<h1>DbEnv::open</h1> +</td> +<td width="1%"> +<a href="../api_cxx/cxx_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a> +</td></tr></table> +<hr size=1 noshade> +<tt> +<h3><pre> +#include <db_cxx.h> +<p> +int +DbEnv::open(const char *db_home, u_int32_t flags, int mode); +</pre></h3> +<h1>Description</h1> +<p>The DbEnv::open method is the interface for opening the Berkeley DB +environment. It provides a structure for creating a consistent +environment for processes using one or more of the features of Berkeley DB. +<p>The <b>db_home</b> argument to DbEnv::open (and file name +resolution in general) is described in +<a href="../ref/env/naming.html">Berkeley DB File Naming</a>. +<p>The <b>flags</b> argument specifies the subsystems that are initialized +and how the application's environment affects Berkeley DB file naming, among +other things. +<p>The <b>flags</b> value must be set to 0 or by bitwise inclusively <b>OR</b>'ing together one or more +of the following values. +<p>As there are a large number of flags that can be specified, they have been +grouped together by functionality. The first group of flags indicate +which of the Berkeley DB subsystems should be initialized: +<p><dl compact> +<p><dt><a name="DB_JOINENV">DB_JOINENV</a><dd>Join an existing environment. This option allows applications to +join an existing environment without knowing which Berkeley DB subsystems +the environment supports. +<p><dt><a name="DB_INIT_CDB">DB_INIT_CDB</a><dd>Initialize locking for the <a href="../ref/cam/intro.html">Berkeley DB Concurrent Data Store</a> +product. In this mode, Berkeley DB provides multiple reader/single writer +access. The only other subsystem that should be specified with the +DB_INIT_CDB flag is DB_INIT_MPOOL. +<p>Access method calls are largely unchanged when using this flag, although +any cursors through which update operations (e.g., <a href="../api_cxx/dbc_put.html">Dbc::put</a>, +<a href="../api_cxx/dbc_del.html">Dbc::del</a>) will be made must have the <a href="../api_cxx/db_cursor.html#DB_WRITECURSOR">DB_WRITECURSOR</a> value +set in the flags parameter to the cursor call that creates the cursor. +See <a href="../api_cxx/db_cursor.html">Db::cursor</a> for more information. +<p><dt><a name="DB_INIT_LOCK">DB_INIT_LOCK</a><dd>Initialize the locking subsystem. This subsystem should be used when +multiple processes or threads are going to be reading and writing a Berkeley DB +database, so that they do not interfere with each other. If all threads +are accessing the database(s) read-only, then locking is unnecessary. +When the DB_INIT_LOCK flag is specified, it is usually necessary to run +the deadlock detector, as well. See <a href="../utility/db_deadlock.html">db_deadlock</a> and +<a href="../api_cxx/lock_detect.html">DbEnv::lock_detect</a> for more information. +<p><dt><a name="DB_INIT_LOG">DB_INIT_LOG</a><dd>Initialize the logging subsystem. This subsystem is used when recovery +from application or system failure is necessary. +<p>The log is stored in one or more files in the environment directory. +Each file is named using the format <i>log.NNNNNNNNNN</i>, where +<i>NNNNNNNNNN</i> is the sequence number of the file within the log. +For further information, see +<a href="../ref/log/limits.html">Log File Limits</a>. +<p>If the log region is being created and log files are already present, the +log files are reviewed and subsequent log writes are appended +to the end of the log, rather than overwriting current log entries. +<p><dt><a name="DB_INIT_MPOOL">DB_INIT_MPOOL</a><dd>Initialize the shared memory buffer pool subsystem. This subsystem is +used whenever the application is using any Berkeley DB access method. +<p><dt><a name="DB_INIT_TXN">DB_INIT_TXN</a><dd>Initialize the transaction subsystem. This subsystem is used when +recovery and atomicity of multiple operations and recovery are important. +The DB_INIT_TXN flag implies the DB_INIT_LOG flag. +</dl> +<p>The second group of flags govern what recovery, if any, is performed when +the environment is initialized: +<p><dl compact> +<p><dt><a name="DB_RECOVER">DB_RECOVER</a><dd>Run normal recovery on this environment before opening it for normal use. +If this flag is set, the DB_CREATE flag must also be set since the regions +will be removed and recreated. +<p><dt><a name="DB_RECOVER_FATAL">DB_RECOVER_FATAL</a><dd>Run catastrophic recovery on this environment before opening it for normal +use. If this flag is set, the DB_CREATE flag must also be set since the +regions will be removed and recreated. +</dl> +<p>A standard part of the recovery process is to remove the existing Berkeley DB +environment and create a new one in which to perform recovery. If the +thread of control performing recovery does not specify the correct region +initialization information (e.g., the correct memory pool cache size), +the result can be an application running in an environment with incorrect +cache and other subsystem sizes. For this reason, the thread of control +performing recovery should either specify correct configuration +information before calling the DbEnv::open method, or it should remove +the environment after recovery is completed, leaving creation of the +correctly sized environment to a subsequent call to DbEnv::open. +<p>All Berkeley DB recovery processing must be single-threaded, that is, only a +single thread of control may perform recovery or access a Berkeley DB +environment while recovery is being performed. As it is not an error to +specify DB_RECOVER for an environment for which no recovery is +required, it is reasonable programming practice for the thread of control +responsible for performing recovery and creating the environment to always +specify the DB_RECOVER flag during startup. +<p>The DbEnv::open function returns successfully if DB_RECOVER +or DB_RECOVER_FATAL is specified and no log files exist, so it is +necessary to ensure all necessary log files are present before running +recovery. For further information, consult <a href="../utility/db_archive.html">db_archive</a> and +<a href="../utility/db_recover.html">db_recover</a>. +<p>The third group of flags govern file naming extensions in the environment: +<p><dl compact> +<!--$Id: m4.env_flags,v 10.9 2000/06/29 22:54:10 bostic Exp $--> +<p><dt><a name="DB_USE_ENVIRON">DB_USE_ENVIRON</a><dd>The Berkeley DB process' environment may be permitted to specify information to +be used when naming files; see <a href="../ref/env/naming.html">Berkeley DB +File Naming</a>. As permitting users to specify which files are used can +create security problems, environment information will be used in file +naming for all users only if the DB_USE_ENVIRON flag is set. +<p><dt><a name="DB_USE_ENVIRON_ROOT">DB_USE_ENVIRON_ROOT</a><dd>The Berkeley DB process' environment may be permitted to specify information to +be used when naming files; see <a href="../ref/env/naming.html">Berkeley DB +File Naming</a>. As permitting users to specify which files are used can +create security problems, if the DB_USE_ENVIRON_ROOT flag is set, +environment information will be used for file naming only for users with +appropriate permissions (e.g., on UNIX systems, users with a user-ID of 0). +</dl> +<p>Finally, there are a few additional, unrelated flags: +<p><dl compact> +<p><dt><a name="DB_CREATE">DB_CREATE</a><dd>Cause Berkeley DB subsystems to create any underlying files, as necessary. +<p><dt><a name="DB_LOCKDOWN">DB_LOCKDOWN</a><dd>Lock shared Berkeley DB environment files and memory mapped databases into memory. +<p><dt><a name="DB_PRIVATE">DB_PRIVATE</a><dd>Specify that the environment will only be accessed by a single process +(although that process may be multi-threaded). This flag has two effects +on the Berkeley DB environment. First, all underlying data structures are +allocated from per-process memory instead of from shared memory that is +potentially accessible to more than a single process. Second, mutexes +are only configured to work between threads. +<p>This flag should not be specified if more than a single process is +accessing the environment, as it is likely to cause database corruption +and unpredictable behavior, e.g., if both a server application and the +Berkeley DB utility <a href="../utility/db_stat.html">db_stat</a> will access the environment, the +DB_PRIVATE flag should not be specified. +<p><dt><a name="DB_SYSTEM_MEM">DB_SYSTEM_MEM</a><dd>Allocate memory from system shared memory instead of from memory backed +by the filesystem. See <a href="../ref/env/region.html">Shared Memory +Regions</a> for more information. +<p><dt><a name="DB_THREAD">DB_THREAD</a><dd>Cause the <a href="../api_cxx/dbenv_class.html">DbEnv</a> handle returned by DbEnv::open to be +<i>free-threaded</i>, that is, useable by multiple threads within a +single address space. +</dl> +<p>On UNIX systems, or in IEEE/ANSI Std 1003.1 (POSIX) environments, all files created by Berkeley DB +are created with mode <b>mode</b> (as described in <b>chmod</b>(2)) and +modified by the process' umask value at the time of creation (see +<b>umask</b>(2)). The group ownership of created files is based on +the system and directory defaults, and is not further specified by Berkeley DB. +If <b>mode</b> is 0, files are created readable and writeable by both +owner and group. On Windows systems, the mode argument is ignored. +<p>The DbEnv::open method either returns a non-zero error value or throws an exception that +encapsulates a non-zero error value on failure, and returns 0 on success. +<h1>Environment Variables</h1> +<p><dl compact> +<p><dt>DB_HOME<dd>The environment variable <b>DB_HOME</b> may be used as the path of +the database home as described in +<a href="../ref/env/naming.html">Berkeley DB File Naming</a>. +</dl> +<h1>Errors</h1> +<p>The DbEnv::open method may fail and throw an exception or return a non-zero error for the following conditions: +<p><dl compact> +<p><dt>EAGAIN<dd>The shared memory region was locked and (repeatedly) unavailable. +</dl> +<p><dl compact> +<p><dt>EINVAL<dd>An invalid flag value or parameter was specified. +<p> +The DB_THREAD flag was specified and spinlocks are not +implemented for this architecture. +<p>The DB_HOME or TMPDIR environment variables were set but empty. +<p>An incorrectly formatted <b>NAME VALUE</b> entry or line was found. +</dl> +<p><dl compact> +<p><dt>ENOSPC<dd>HP-UX only: a previously created Berkeley DB environment for this process still +exists. +</dl> +<p>The DbEnv::open method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods. +If a catastrophic error has occurred, the DbEnv::open method may fail and either +return <a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a> or throw an exception encapsulating +<a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a>, in which case all subsequent Berkeley DB calls will fail +in the same way. +<h3>Class</h3> +<a href="../api_cxx/dbenv_class.html">DbEnv</a> +<h1>See Also</h1> +<a href="../api_cxx/env_close.html">DbEnv::close</a>, +<a href="../api_cxx/env_open.html">DbEnv::open</a>, +<a href="../api_cxx/env_remove.html">DbEnv::remove</a>, +<a href="../api_cxx/db_err.html">DbEnv::err</a>, +<a href="../api_cxx/env_strerror.html">DbEnv::strerror</a>, +<a href="../api_cxx/env_version.html">DbEnv::version</a>, +<a href="../api_cxx/env_set_cachesize.html">DbEnv::set_cachesize</a>, +<a href="../api_cxx/env_set_errcall.html">DbEnv::set_errcall</a>, +<a href="../api_cxx/env_set_errfile.html">DbEnv::set_errfile</a>, +<a href="../api_cxx/env_set_error_stream.html">DbEnv::set_error_stream</a>, +<a href="../api_cxx/env_set_errpfx.html">DbEnv::set_errpfx</a>, +<a href="../api_cxx/env_set_flags.html">DbEnv::set_flags</a>, +<a href="../api_cxx/env_set_mutexlocks.html">DbEnv::set_mutexlocks</a>, +<a href="../api_cxx/env_set_paniccall.html">DbEnv::set_paniccall</a>, +and +<a href="../api_cxx/env_set_verbose.html">DbEnv::set_verbose</a>. +</tt> +<table><tr><td><br></td><td width="1%"> +<a href="../api_cxx/cxx_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a> +</td></tr></table> +<p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font> +</body> +</html> |