init.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: init.so,v 1.6 2005/10/19 19:11:20 bostic Exp $])

m4_ref_title(m4_db Replication,
    Initializing a new site,, rep/mastersync, rep/bulk)

m4_p([dnl
By default, adding a new site to a replication group only requires the
client to join.  m4_db will automatically perform internal
initialization from the master to the client, bringing the client into
sync with the master.])

m4_p([dnl
However, depending on the network and infrastructure, it can be
advantageous in a few instances to use a "hot backup" to initialize a
client into a replication group.  Clients not wanting to automatically
perform internal initialization should call the m4_refT(rep_set_config)
with the m4_ref(DB_REP_CONF_NOAUTOINIT) flag.  This configuration flag
causes m4_db to return m4_ref(DB_REP_JOIN_FAILURE) to the application's
m4_refT(rep_message) instead of performing internal initialization.])

m4_p([dnl
To use a hot backup to initialize a client into a replication group,
perform the following steps:])

m4_nlistbegin

m4_nlist([dnl
Do an archival backup of the master's environment, as described in
m4_link(M4RELDIR/ref/transapp/archival, [Database and log file
archival]).  The backup can either be a conventional backup or a hot
backup.])

m4_nlist([dnl
Copy the archival backup into a clean environment directory on the
client.])

m4_nlist([dnl
Run catastrophic recovery on the client's new environment, as described
in m4_link(M4RELDIR/ref/transapp/recovery, [Recovery procedures]).])

m4_nlist([dnl
Reconfigure and reopen the environment as a client member of the
replication group.])

m4_nlistend

m4_p([dnl
If copying the backup to the client takes a long time relative to the
frequency with which log files are reclaimed using the
m4_ref(db_archive) utility or the m4_refT(log_archive), it may be
necessary to suppress log reclamation until the newly restarted client
has "caught up" and applied all log records generated during its
downtime.])

m4_p([dnl
As with any m4_db application, the database environment must be in a
consistent state at application startup.  This is most easily assured
by running recovery at startup time in one thread or process; it is
harmless to do this on both clients and masters even when not strictly
necessary.])

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