Spin Alteration Monitor

In data processing, the File Deterioration Monitor (FAM) is a subsystem under Unix/Linux of which the goal is to prevent the applications as soon as certain files are modified.

In French, the translation of this term could be Moniteur of modifications of file . It happens that the misleading translation is " Monitor of deterioration of fichier" , but the term deterioration lends to confusion.

Presentation

This so known software under the name of sgi_fam provides a subsystem (developed by SGI) for the operating systems based on Unix (linux and others). Subsystem FAM prevents other applications as soon as certain files are modified.

That simplifies of much the task of the programmers for the customer applications, if not it would be necessary to program a repetitive reading of the disc to detect any change, which would be penalizing in times of development and, more important, for the performances of the applications.

For example, a Gestionnaire of files is prevented when files are modified and it can refresh if necessary the representation of this file in the graphical interface.

Software components and parameter settings

Subsystem FAM is composed of two parts:

  • famd - the Demon FAM which manages the Notification S and treats the requests. The administrators can configure it by publishing the file etc/fam.conf

One can amongst other things parameterize the time of polling (cyclic examination) for NFS (parameter nfs_polling_interval )

  • libfam - Library FAM: the API of interface with the applications customer

Applications on other computers can use this subsystem in 2 ways

  • indirectly, via etc/inetd (see,)
  • directly (in this precise case, it is necessary to correctly parameterize the parameter local_only of etc/fam.conf ).

Equivalent under Windows of this subsystem

FindFirstChangeNotification or FindNextChangeNotification is 2 functions of the API Windows, which are the equivalent of the libfam of Unix.

Related articles

  • the other parameter settings of NFS are done via the file etc Fstab
  • Portmap: demon necessary so that demon FAM functions

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