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Configuring Database Server settings Database settings
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ILEMAKER SERVER 9 HELP 69
Cache flushing operation
In FileMaker Server, the cache is constantly being flushed. The cache flushing routine scans the
cache, looking for pages that have changed. FileMaker Server inspects up to 1/60th of the cache
and writes any changed pages it discovers to the disk. The process repeats continuously, writing 1/
60 of the cache to disk every second, even during scheduled backups.
For example, in a 64 MB cache FileMaker Server will inspect up to 1/60th of the cache, or a little
more than a megabyte, and flush all of the changed records it finds. It will then wait a second and
begin again, inspecting up to 1/60th of the cache, looking for changed records. This method of
flushing the cache distributes writing to the hard disk over the span of a minute.
By default, the cache flush mechanism will attempt to scan the entire cache in a minute. In most
cases this means all cached changes on the server will be no more than one minute old, although
database size and hard disk speed can affect these results.
To change this behavior and spread the cache flushing over a longer period of time, increase the
value of the Cache flush distribution interval (hh:mm). Unsaved changes in FileMaker Server will
be no older than the interval you specify. FileMaker Server reduces the amount of data it inspects
every second, but never less than 128 KB per second.
Before increasing the cache flushing interval, the administrator should carefully consider the risk of
data loss in the event of a computer failure. Locations that require maximum performance and are
less concerned about the potential for lost data can use a longer cache flush distribution interval,
while locations that want maximum data integrity should use a smaller cache flush distribution
interval.
For example, if the value is set to 10 minutes with a 64 MB cache, the engine will inspect 1/600th of
the cache each second, or about 110 KB of cache (less than the minimum, so the engine will
actually inspect 128 KB of cache), and write only the changed data to disk. However, if this interval
is set to 10 minutes with a 500 MB cache, it will only inspect 853 KB as opposed to the default value
of 1/60th of the cache, or 8.5 MB. Used this way, the server can distribute its disk writing over time,
and therefore allow the server CPU a higher priority to service client
requests, as it will take much
less time to inspect 853 KB compared to 8.5 MB.
Related topic
Database settings (page 67)