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Originally Posted by
ckwan
1. Why most of time the File Cache in the memory seems constantly 100%?
It is memory which the system has borrowed to store file contents temporarily -- if you ask for the same file twice, reading it the second time is as fast as retrieving it from memory. It's just as good as Free, the system will give it up whenever needed.
There's at least two reasons why cache would be so high -- either this server is very idle, letting all memory gradually trickle into cache, or there's high levels of disk activity which push free memory into cache much faster.
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But why this is not happen in Datastage 2 and 3?
They are experiencing different loads. Maybe they have less disk activity, or maybe they're hosting RAM-hungry programs that leave very little room for cache (which is a bad thing, by the way -- cache is good for you).
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btw, Is File Cache is part of the memory or it is separated from memory ?
Cache is part of memory. The system has borrowed it to store file contents, but gives it back just as easily.