logfile.so

berkeley db 4.6.21的源码。berkeley db是一个简单的数据库管理系统

m4_comment([$Id: logfile.so,v 11.9 2002/11/13 21:49:24 bostic Exp $])

m4_ref_title(m4_tam Applications,
    Log file removal,
    @log file removal,
    transapp/archival, transapp/recovery)

m4_p([dnl
The fourth component of the infrastructure, log file removal, concerns
the ongoing disk consumption of the database log files.  Depending on
the rate at which the application writes to the databases and the
available disk space, the number of log files may increase quickly
enough so that disk space will be a resource problem.  For this reason,
you will periodically want to remove log files in order to conserve disk
space.  This procedure is distinct from database and log file archival
for catastrophic recovery, and you cannot remove the current log files
simply because you have created a database snapshot or copied log files
to archival media.])

m4_p([dnl
Log files may be removed at any time, as long as:])
m4_bulletbegin
m4_bullet([the log file is not involved in an active transaction.])
m4_bullet([a checkpoint has been written subsequent to the log file's
creation.])
m4_bullet([the log file is not the only log file in the environment.])
m4_bulletend

m4_p([dnl
If you are preparing for catastrophic failure, you will want to copy
the log files to archival media before you remove them as described in
m4_link(archival, Database and log file archival).])

m4_p([dnl
If you are not preparing for catastrophic failure, any one of the
following methods can be used to remove log files:])

m4_nlistbegin

m4_nlist([dnl
Run the standalone m4_ref(db_archive) utility with the m4_option(d)
option, to remove any log files that are no longer needed at the time
the command is executed.])

m4_nlist([dnl
Call the m4_refT(log_archive) from the application, with the
m4_ref(DB_ARCH_REMOVE) flag, to remove any log files that are no longer
needed at the time the call is made.])

m4_nlist([dnl
Call the m4_refT(dbenv_set_flags) from the application, with the
m4_ref(DB_LOG_AUTOREMOVE) flag, to remove any log files that are no
longer needed on an ongoing basis.  With this configuration, m4_db will
automatically remove log files, and the application will not have an
opportunity to copy the log files to backup media.])

m4_nlistend

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