Re: Fav. Urban Legend...Mem vs Disk

That does add an interesting element to
the version 9 "max_aggregate_pga"
(or max_pga_aggregate or pga_max_aggregate .. permute as needed until the database restarts because I can't remember the order the words are in).

If we set

    pga_aggregate_max to 500MB
then Oracle tries to allocate all working sizes (hash, sort, bitmap create/merge)
on demand so that the current sum doesn't exceed the aggregate max.

Presumably, however, it does this by
"looking at" the v$sesstat figures of current sessions, and tracking their current
pga memory size, NOT their pga max memory size - but we all know that the O/S often still reports the process's memory as the pga max, long after Oracle has issued the free() call to release it.

So how long will it be before we get -

    I've set the pga_agg_max to 500MB,
    but when I add up the memory from
    'ps', or 'top' Oracle is obviously ignoring     the limit.

Jonathan Lewis
http://www.jlcomp.demon.co.uk

Next Seminar - UK, April 3rd - 5th
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Host to The Co-Operative Oracle Users' FAQ http://www.jlcomp.demon.co.uk/faq/ind_faq.html

Author of:
Practical Oracle 8i: Building Efficient Databases

-----Original Message-----
To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com> Date: 22 March 2002 07:58

|UNIX problem ? If memory is allocated from the HEAP it is never
really returned
|to the OS when we do a free. The free only happens when the process
exits. So
|the question is: Do we need the 200 MB or is it somekind of memory
leak ? If we
|need the 200 MB, remember that we are running on a demand paging
systems these
|days. So we only bring in memory what we need, you need to think
about your
|swap space though .......
|
|Anjo.
|
|

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