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pmap - anon pages

From: hopehope_123 <hopehope_123_at_yahoo.com>
Date: 28 Jul 2005 04:01:05 -0700
Message-ID: <1122545396.039818.231160@g47g2000cwa.googlegroups.com>


Hi,
This is a datawarehouse system , and parallel query is mostly used. I am trying to locate the oracle pga memory allocation inside the process in
order to size my systems memory requirements. I have read the documents in
metalink but i believe i could not find the answer of the following questions:
When i monitor an oracle process by using pmap , i can easily see shared memory
, stack , heap , libraries. By using this output i issue some sqls and check
pmap output .
example queries:
SELECT /*+PARALLEL(T,32)*/ * FROM TOLGA2 t order by 1 SELECT /*+noPARALLEL(T)*/ * FROM TOLGA2 t order by 1 i was told that oracle parallel query bypasses the oracle buffer cache and
uses process memory instead.
Based on these backgrounds ,
1. For the parallel query , i have tried various sort_Area_size parameters with
manual workarea management in order to see its effect in pga memory allocation
(and pmap output ) . What i see in pmap output is , lots of anon
(anonymous

pages) are allocated instead of heap. But according to the documents pga is
allocated inside the heap. (Anon page is a page that is not associated with a
particular vnode, or file/directory )Is the data stored inside this anon pages?
2. for the nonparallel query , i assume that the data blocks now ara cached
inside the oracle sga which is in shared memory but i can see the same anon
page allocation pattern here. Why does the process allocates anon pages like

parallel query case although data is cached inside the shared memory
(and it

is also mapped in process)
Kind Regards,
tolga Received on Thu Jul 28 2005 - 06:01:05 CDT

Original text of this message

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