[buffers]
pagesize=1 or 8
This value represents the number of adjacent 512 byte disk sectors that are read and written simultaneously and kept contiguous in memory.
You must ensure that pagesize is large enough so that an index node can be contained in a single page. Currently, if your index node size exceeds the page size DP4 will crash.
At least on computers using Intel Processors, operating systems usually cache disk information in 4K chunks, and therefore all other things being equal it is a good idea for programs to do the same. Unfortunately 4K can be inconviently large for DP4. For example the index file of a DP4 database normally uses 512 byte records (though this can now be changed), so using a page size of 8 can mean that information that could usefully remain in the cache is thrown out in favour of information that is not needed but is on the same page as information that is. Once there are enough disk buffers the benefit of using the operating system's natural page size outweighs the benefit of keeping the best set of sectors. The default pagesize is 1 if less than 1 Megabyte of cache is allocated to DP4, and 8 otherwise.
In release 4.622 DP4 will force the page size to the "natural" value as indicated by the operating system if the bypass_cache=2 setting is enabled.