Muq Dbfiles Wrapup

Other adminstratively useful tidbits of information about Muq dbfile files:

• Muq dbfiles are 64-bit throughout on all supported machines, including Intel/x86.
• Muq dbfiles are big-endian or little-endian according to the convention used by the host machine. (This is necessary for rational memory-mapped file sharing.) Future versions of Muq will automatically convert between byte orders as needed, but this is not yet implemented. At present, Muq dbfiles cannot be transported between machines with different byte sexes.
• You will eventually be able to mount and dismouht Muq dbfiles in a server about as freely as you can mount and dismount disk partitions in unix. This is not yet implemented, however.
• When the Muq server does backups, all dbfiles are saved at the same time, and all receive the same generation number.
• Beyond the above, the Muq server also keeps "logarithmic" backups: It attempts to as good an approximation as possible to keep the most recent second, fourth, eighth, sixteenth and so forth backups. This provides a scattering of older fallback dbs as insurance against something being clobbered and not missed for weeks, without filling up the disk with inordinate numbers of backups. If you don't want logarithmic backups to be kept, set the internal Muq variable .muq.logarithmicBackups to NIL.
• Once a dbfile receives a numeric generation number, the Muq server will not touch it again in the course of normal operations. (The sole exception being to delete it when it gets too old, to save disk space.) You can delete any or all of the numbered backup files at any time if you like. Just don't clobber the RUNNING files if you care about the current server run, or the CURRENT files if you have any ambition to restart from the current point should the running server crash.
• The number of consecutive recent backups kept is controlled by the internal .muq.consecutiveBackupsToKeep variable. Six is a good number; Two or three is risky. If you have effectively unlimited disk space, feel free to set this value to some large number like a billion.
• Muq can work with uncompressed .db files, or files compressed by any of gzip, lzop or bzip2. Muq dbfiles, like almost all binary database formats, compress very well, typically by a factor of ten or so -- so keeping inactive dbfiles compressed can save lots of diskspace. gzip is the typical compressio program these days, lzop is several times faster at the cost of compressing perhaps 30% less, and bzip2 provides the best compression, but may not work well with binary files such as Muq uses. Muq will look for these programs in /bin, /usr/bin, and /usr/local/bin. If they are elsewhere on your system, you may setenv one of the Unix environment variables MUQ_GZIP, MUQ_LZOP or MUQ_BZIP2 to the appropriate path, perhaps /home/me/bin/gzip. To disable use of one (or all) of these programs, setenv the corresponding environment variable to the empty string.
• The interval between backups is controlled by the internal Muq variable .muq.millisecsBetweenBackups. It can be anything from minutes to years, at your discretion. Once a day (86400000) is probably a reasonable choice on a stable production server; Perhaps once an hour (3600000) if critical work is being done or crashes are a problem.

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