Import BSDDB 4.7.25 (as of svn r89086)
This commit is contained in:
Zachary Ware
131
docs_src/log/env_log_set_config.so
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131
docs_src/log/env_log_set_config.so
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m4_comment([$Id])
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define(M4PAGELOCAL,
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[dbenv_log_set_config, dbenv_log_get_config,
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DB_LOG_DIRECT, DB_LOG_DSYNC, DB_LOG_AUTO_REMOVE,
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DB_LOG_BUFFER_FULL, DB_LOG_IN_MEMORY, DB_LOG_ZERO])
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include(m4/m4.seealso)
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m4_pf_header(m4_ref(dbenv_log_set_config),
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ifelse(M4API, C_API, [dnl
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int
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DB_ENV-__GT__log_set_config(DB_ENV *dbenv, u_int32_t flags, int onoff);
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m4_blank
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int
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DB_ENV-__GT__log_get_config(DB_ENV *dbenv, u_int32_t which, int *onoffp);
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])
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ifelse(M4API, CXX_API, [dnl
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int
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DbEnv::log_set_config(u_int32_t flags, int onoff);
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m4_blank
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int
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DbEnv::log_get_config(u_int32_t which, int *onoffp)
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]))
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m4_p([dnl
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The m4_refT(dbenv_log_set_config) configures the m4_db logging
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subsystem.])
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m4_scope_env(dbenv_log_set_config)
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m4_when_any(dbenv_log_set_config)
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m4_return(dbenv_log_set_config, std)
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m4_parambegin
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m4_param(flags, [dnl
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m4_sf_or_must
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m4_tagbegin
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m4_idefz([turn off system @buffering for log files])
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m4_tag(m4_idef(DB_LOG_DIRECT), [dnl
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Turn off system buffering of m4_db log files to avoid double caching.
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m4_scope_dbenv_flags(dbenv_log_set_config, DB_LOG_DIRECT, config)
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m4_env_flags_any(DB_LOG_DIRECT)])
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m4_idefz([turn off system @buffering for log files])
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m4_tag(m4_idef(DB_LOG_DSYNC), [dnl
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Configure m4_db to flush log writes to the backing disk before returning
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from the write system call, rather than flushing log writes explicitly
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in a separate system call, as necessary. This is only available on some
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systems (for example, systems supporting the m4_posix1_name standard
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O_DSYNC flag, or systems supporting the Windows FILE_FLAG_WRITE_THROUGH
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flag). This flag may result in inaccurate file modification times and
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other file-level information for m4_db log files. This flag may offer
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a performance increase on some systems and a performance decrease on
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others.
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m4_scope_dbenv_flags(dbenv_log_set_config, DB_LOG_DSYNC, config)
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m4_env_flags_any(DB_LOG_DSYNC)])
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m4_idefz([automatic @log file removal])
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m4_tag(m4_idef(DB_LOG_AUTO_REMOVE), [dnl
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If set, m4_db will automatically remove log files that are no longer
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needed.
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m4_p([dnl
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Automatic log file removal is likely to make catastrophic recovery
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impossible.])
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m4_p([dnl
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Replication applications will rarely want to configure automatic log
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file removal as it increases the likelihood a master will be unable to
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satisfy a client's request for a recent log record.])
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m4_scope_env_flags(dbenv_log_set_config, DB_LOG_AUTO_REMOVE)
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m4_env_flags_any(DB_LOG_AUTO_REMOVE)])
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m4_idefz([in memory @logs])
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m4_tag(m4_idef(DB_LOG_IN_MEMORY), [dnl
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If set, maintain transaction logs in memory rather than on disk. This
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means that transactions exhibit the ACI (atomicity, consistency, and
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isolation) properties, but not D (durability); that is, database
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integrity will be maintained, but if the application or system fails,
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integrity will not persist. All database files must be verified and/or
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restored from a replication group master or archival backup after
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application or system failure.
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m4_p([dnl
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When in-memory logs are configured and no more log buffer space is
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available, m4_db methods may return an additional error value,
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m4_idef(DB_LOG_BUFFER_FULL). When choosing log buffer and file sizes
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for in-memory logs, applications should ensure the in-memory log buffer
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size is large enough that no transaction will ever span the entire
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buffer, and avoid a state where the in-memory buffer is full and no
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space can be freed because a transaction that started in the first log
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"file" is still active.])
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m4_scope_env_flags(dbenv_log_set_config, DB_LOG_IN_MEMORY, config)
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m4_env_flags_open(DB_LOG_IN_MEMORY, before)])
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m4_idefz([pre-zero @log files])
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m4_tag(m4_idef(DB_LOG_ZERO), [dnl
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If set, zero all pages of a log file when that log file is created. This
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has shown to provide greater transaction throughput in some environments.
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The log file will be zeroed by the thread which needs to re-create the new log
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file. Other threads may not write to the log file while this is happening.
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m4_scope_env_flags(dbenv_log_set_config, DB_LOG_ZERO, config)
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m4_env_flags_open(DB_LOG_ZERO, before)])
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m4_tagend])
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m4_param(onoff, [dnl
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If the m4_arg(onoff) parameter is zero, the specified flags are cleared;
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otherwise they are set.])
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m4_paramend
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m4_err(dbenv_log_set_config, einval)
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m4_pf_description(m4_ref(dbenv_log_get_config))
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m4_p([dnl
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The m4_refT(dbenv_log_get_config) returns whether the specified m4_arg(which)
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parameter is currently set or not.])
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m4_when_any(dbenv_log_get_config)
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m4_return(dbenv_log_get_config, std)
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m4_parambegin
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m4_param(which, [dnl
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The m4_arg(which) parameter is the message value for which configuration
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is being checked.])
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m4_param_co(onoffp, [dnl
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configuration of the specified m4_arg(which) parameter],, [dnl
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If the returned m4_arg(onoff) value is zero, the parameter is off;
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otherwise on.])
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m4_paramend
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m4_seealso(DbEnv)
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m4_page_footer
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