SYBASE 10 Memory usage compare with 4.0.1 
Author Message
 SYBASE 10 Memory usage compare with 4.0.1


Quote:
'tonster) writes:

> We are migrating to SYBASE SYS10 very shortly from 4.0.1 SYBASE servers.

> I'm interested primarily with how SYBASE SYS10 handles increase in memory
> as oppose to 4.0.1 or any 4.x version of SYBASE.  We have a database of
> about 350-400 concurrently users, 10,000 transaction a day.  Our current
> version of SYBASE doesn't seem to benefit from increases in memory.  we
> have
> 96 megs allocated for the server and when we bumped it up to 256MEG, the
> entire machine froze and the server became useless.

> Do you have any suggestions on how much memory to allocate for the
> SYBASE10
> server or how do we find that right number?

4.0 seems like a long time ago. Didn't pre-4.8 versions of the server have
a bug, whereby allocating more than 32MB of memory to them caused them to
lose track of memory allocation --- resulting in *worse* performance than
if they had less than 32MB?

--

I boycott companies using mass Internet advertising.
    Engineers think equations approximate reality.
    Physicists think reality approximates the equations.
    Mathematicians never make the connection.



Sun, 06 Apr 1997 11:43:27 GMT
 SYBASE 10 Memory usage compare with 4.0.1


Quote:
>4.0 seems like a long time ago. Didn't pre-4.8 versions of the server have
>a bug, whereby allocating more than 32MB of memory to them caused them to
>lose track of memory allocation --- resulting in *worse* performance than
>if they had less than 32MB?

It's not a bug.  It's described in the trouble shooting guide.  In pre-4.8,
the cache's hashing method uses a fixed number of buckets, with linked list
for each bucket (is it called open hasing?).  The more the memory, the more
likely that two pages will be hashed to the same bucket.  So lots of memory
may result in hashing buckets holding long linked lists, and hence the
performance decrease.

Starting from 4.8, the number of hashing buckets is calculated at runtime
to ensure that usually no more than 2 pages will be hashed to the same
bucket.  So more memory will never decrease performance, although it may
not neccessarily improve performance.

--

Q Vincent Yin                   |       Repeat

                                |       Until 0 = 1;



Sun, 06 Apr 1997 21:59:51 GMT
 SYBASE 10 Memory usage compare with 4.0.1

   >4.0 seems like a long time ago. Didn't pre-4.8 versions of the server have

Yeah, we only have 4.0.1 and the next version is SYS10. :-) great project in
migrating it though.

   >a bug, whereby allocating more than 32MB of memory to them caused them to
   >lose track of memory allocation --- resulting in *worse* performance than
   >if they had less than 32MB?

   It's not a bug.  It's described in the trouble shooting guide.  In pre-4.8,
   the cache's hashing method uses a fixed number of buckets, with linked list
   for each bucket (is it called open hasing?).  The more the memory, the more
   likely that two pages will be hashed to the same bucket.  So lots of memory
   may result in hashing buckets holding long linked lists, and hence the
   performance decrease.

Yes, this is the problem I was refering where our 4.0.1 server almost died when
we allocated 256MEG for it.

   Starting from 4.8, the number of hashing buckets is calculated at runtime
   to ensure that usually no more than 2 pages will be hashed to the same
   bucket.  So more memory will never decrease performance, although it may
   not neccessarily improve performance.

So SYS10 will at least behave reasonably when we throw more memory at it?

ALSO,

Anyone have experience with running SYBASE SYS10 on SGI platform?  Have you play
around with different memory configurations and what are the final results?  How
did you decide on a specific memory config?

Thank you ..

--
***********************************************************************
    Tony "Might be getting a life" Tam :-]

***********************************************************************



Tue, 08 Apr 1997 23:48:33 GMT
 
 [ 3 post ] 

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