oracle cache fusion against informix XPS?

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utkanbir - 31 Jul 2003 07:03 GMT

Hi Gurus,

I was an Informix man , but my last job needs Oracle skills which i
have no experience. My question is about oracle real application
clusters. I know that
oracle's shared everything architecture uses Dlm (distributed lock
manager ) and for large installations this was a problem. But all the
oracle white papers say this was history. Their cache fusion tech.
solved all the problems.
Is there any one who can comment on this?

Kind Regards,
hope

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A Blonde - 31 Jul 2003 12:08 GMT

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sending to informix-list

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Mark Townsend - 31 Jul 2003 16:31 GMT

> Is there any one who can comment on this?

Sure - here to help :-)

The DLM was never really that big a problem, although people liked to
think it was. The real issue was as follows

Setup
-----
Block A on disk
Block A loaded into memory on Node 1
Block A loaded into memory on Node 2
Change to Block A in memory on Node 1
Change or Read of Block A in Memory on Node 2 requires a synchronization

Previous Behaviour
------------------
1) Node 1 would write changed block to disk
2) Node 2 would read changed block from disk for the query
This was known as a 'ping', and IO could quickly become a bottle neck if
you didn't design your app to reduce the number of cross node 'pings' of
data. And after the re-design, you would need to then partition your
data to make the design work

Now, with Cache Fusion
----------------------
1) Node 1 pokes the changed block from it's memory to Node 2's memory
No IO, no need to re-design app, partition data etc

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