Atomic Update

[Jan Grant]

On Sun, 10 Dec 2006, White Hat wrote:

> I am not sure what the correct procedure is to do an
> atomic update.
> 
> Scenario:
> 
> 1) Download database-1. This database is going to
> replace an identically named database. Since I cannot
> shut down the program that is using this database,
> what would be the best way to insert the new database.
> I was thinking that I could use the 'mv' command as
> opposed to 'cp', but I am not sure.

You don't mention what software is consuming your database file. It's 
true that "mv" within a filesystem is an atomic operation, it is not 
necessarily the case that an arbitrary program that is using the target 
file will notice the change; for instance, if the target program just 
has an open filehandle to the file, then it would need to reopen the 
file once the replacement had taken place.

-- 
jan grant, ISYS, University of Bristol. http://www.bris.ac.uk/
Tel +44 (0)117 3317661   http://ioctl.org/jan/
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