Frequently Asked Questions

Nov 16, 2019 - 08:33pm

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What do the "page discards", "pages read", and "reclaims" numbers mean?

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Created On: 5 Mar 1999 1:27 pm
Last Edited: 4 Mar 2013 11:33 am

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The Memory Usage section of the control panel displays the number of page discards/reads/reclaims since the server reset. The significance of these figures may not be immediately obvious.

Answer

These terms represent an event where Web Crossing had to discard items that were cached in memory because the cache was full. A modest number of page discards is perfectly normal because the cache can never contain everything. Each page discard represents a small loss off performance so ideally you will keep page discards relatively low within the limitations imposed by the amount of RAM available for Web Crossing to use. Limiting page discards to a few thousand in a 24-hour period is a reasonable goal, but not always achievable.

If page discards are high, increase the memory allocated to the particular setting (small object heap or disk cache). The number for memory allocation is kilobytes, so if you enter 1024 you are allocating one megabyte of memory.

After each change, monitor page discards every 24 hours for a few days and change again as necessary until a reasonable compromise is reached between performance and availability of RAM for other processes that may be running on the same server.

It is important to note that setting a disk cache too high is ineffective and may cause worse performance than setting it too low (if you end up using virtual memory/page file). A good starting point for disk cache memory allocation is RAM equal to approximately one-third of the size of the database for verions 3.1 or earlier, and about 50% for version 4.0 and higher (depending on services used, and complexity and efficiency of custom macros).

Other memory topics here