limits.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: limits.so,v 10.26 2004/08/13 03:48:05 bostic Exp $])

m4_ref_title(Logging Subsystem,
    Log file limits, @log file limits, log/config, mp/intro)

m4_p([dnl
Log filenames and sizes impose a limit on how long databases may be
used in a m4_db database environment.  It is quite unlikely that an
application will reach this limit; however, if the limit is reached,
the m4_db environment's databases must be dumped and reloaded.])

m4_p([dnl
The log filename consists of m4_bold(log.) followed by 10 digits, with
a maximum of 2,000,000,000 log files.  Consider an application performing
6000 transactions per second for 24 hours a day, logged into 10MB log
files, in which each transaction is logging approximately 500 bytes of data.
The following calculation:])

m4_indent([(10 * 2^20 * 2000000000) / (6000 * 500 * 365 * 60 * 60 * 24) = ~221])

m4_p([dnl
indicates that the system will run out of log filenames in roughly 221
years.])

m4_p([dnl
There is no way to reset the log filename space in m4_db.  If your
application is reaching the end of its log filename space, you must do
the following:])

m4_nlistbegin

m4_nlist([dnl
Archive your databases as if to prepare for catastrophic failure (see
m4_link(M4RELDIR/ref/transapp/archival, [Database and log file archival])
for more information).])

m4_nlist([dnl
Reset the database's log sequence numbers (see the m4_option(r) option
to the m4_ref(db_load) utility for more information).])

m4_nlist([dnl
Remove all of the log files from the database environment.  (This is the
only situation in which all the log files are removed from an environment;
in all other cases, at least a single log file is retained.)])

m4_nlist([Restart your application.])

m4_nlistend

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