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Performance Management Guide


Using sync/fsync Calls

If a file is opened with O_SYNC or O_DSYNC, then each write will cause the data for that write to be flushed to disk before the write returns. If the write causes a new disk allocation (the file is being extended instead of overwriting an existing page), then that write will also cause a corresponding JFS log write.

Forced synchronization of the contents of real memory and disk takes place in several ways:

A sync operation has several effects, aside from its small CPU consumption:


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