m4_comment([$Id])

define(M4PAGELOCAL,
	[dbenv_log_set_config, dbenv_log_get_config,
	DB_LOG_DIRECT, DB_LOG_DSYNC, DB_LOG_AUTO_REMOVE,
	DB_LOG_BUFFER_FULL, DB_LOG_IN_MEMORY, DB_LOG_ZERO])
include(m4/m4.seealso)

m4_pf_header(m4_ref(dbenv_log_set_config),
ifelse(M4API, C_API, [dnl
int
DB_ENV-__GT__log_set_config(DB_ENV *dbenv, u_int32_t flags, int onoff);
m4_blank
int
DB_ENV-__GT__log_get_config(DB_ENV *dbenv, u_int32_t which, int *onoffp);
])
ifelse(M4API, CXX_API, [dnl
int
DbEnv::log_set_config(u_int32_t flags, int onoff);
m4_blank
int
DbEnv::log_get_config(u_int32_t which, int *onoffp)
]))

m4_p([dnl
The m4_refT(dbenv_log_set_config) configures the m4_db logging
subsystem.])

m4_scope_env(dbenv_log_set_config)
m4_when_any(dbenv_log_set_config)
m4_return(dbenv_log_set_config, std)

m4_parambegin
m4_param(flags, [dnl
m4_sf_or_must

m4_tagbegin

m4_idefz([turn off system @buffering for log files])
m4_tag(m4_idef(DB_LOG_DIRECT), [dnl
Turn off system buffering of m4_db log files to avoid double caching.
m4_scope_dbenv_flags(dbenv_log_set_config, DB_LOG_DIRECT, config)
m4_env_flags_any(DB_LOG_DIRECT)])

m4_idefz([turn off system @buffering for log files])
m4_tag(m4_idef(DB_LOG_DSYNC), [dnl
Configure m4_db to flush log writes to the backing disk before returning
from the write system call, rather than flushing log writes explicitly
in a separate system call, as necessary.  This is only available on some
systems (for example, systems supporting the m4_posix1_name standard
O_DSYNC flag, or systems supporting the Windows FILE_FLAG_WRITE_THROUGH
flag).  This flag may result in inaccurate file modification times and
other file-level information for m4_db log files.  This flag may offer
a performance increase on some systems and a performance decrease on
others.
m4_scope_dbenv_flags(dbenv_log_set_config, DB_LOG_DSYNC, config)
m4_env_flags_any(DB_LOG_DSYNC)])

m4_idefz([automatic @log file removal])
m4_tag(m4_idef(DB_LOG_AUTO_REMOVE), [dnl
If set, m4_db will automatically remove log files that are no longer
needed.
m4_p([dnl
Automatic log file removal is likely to make catastrophic recovery
impossible.])
m4_p([dnl
Replication applications will rarely want to configure automatic log
file removal as it increases the likelihood a master will be unable to
satisfy a client's request for a recent log record.])
m4_scope_env_flags(dbenv_log_set_config, DB_LOG_AUTO_REMOVE)
m4_env_flags_any(DB_LOG_AUTO_REMOVE)])

m4_idefz([in memory @logs])
m4_tag(m4_idef(DB_LOG_IN_MEMORY), [dnl
If set, maintain transaction logs in memory rather than on disk.  This
means that transactions exhibit the ACI (atomicity, consistency, and
isolation) properties, but not D (durability); that is, database
integrity will be maintained, but if the application or system fails,
integrity will not persist.  All database files must be verified and/or
restored from a replication group master or archival backup after
application or system failure.
m4_p([dnl
When in-memory logs are configured and no more log buffer space is
available, m4_db methods may return an additional error value,
m4_idef(DB_LOG_BUFFER_FULL).  When choosing log buffer and file sizes
for in-memory logs, applications should ensure the in-memory log buffer
size is large enough that no transaction will ever span the entire
buffer, and avoid a state where the in-memory buffer is full and no
space can be freed because a transaction that started in the first log
"file" is still active.])
m4_scope_env_flags(dbenv_log_set_config, DB_LOG_IN_MEMORY, config)
m4_env_flags_open(DB_LOG_IN_MEMORY, before)])

m4_idefz([pre-zero @log files])
m4_tag(m4_idef(DB_LOG_ZERO), [dnl
If set, zero all pages of a log file when that log file is created.  This
has shown to provide greater transaction throughput in some environments.
The log file will be zeroed by the thread which needs to re-create the new log
file.  Other threads may not write to the log file while this is happening.
m4_scope_env_flags(dbenv_log_set_config, DB_LOG_ZERO, config)
m4_env_flags_open(DB_LOG_ZERO, before)])
m4_tagend])

m4_param(onoff, [dnl
If the m4_arg(onoff) parameter is zero, the specified flags are cleared;
otherwise they are set.])
m4_paramend

m4_err(dbenv_log_set_config, einval)

m4_pf_description(m4_ref(dbenv_log_get_config))
m4_p([dnl
The m4_refT(dbenv_log_get_config) returns whether the specified m4_arg(which)
parameter is currently set or not.])

m4_when_any(dbenv_log_get_config)

m4_return(dbenv_log_get_config, std)

m4_parambegin
m4_param(which, [dnl
The m4_arg(which) parameter is the message value for which configuration
is being checked.])
m4_param_co(onoffp, [dnl
configuration of the specified m4_arg(which) parameter],, [dnl
If the returned m4_arg(onoff) value is zero, the parameter is off;
otherwise on.])
m4_paramend

m4_seealso(DbEnv)
m4_page_footer