RE: sorting and pga for non-mts

Hi Deepak,

Sort memory resides in the "cursor work heap", which is part of the UGA, which part of the PGA in non-MTS connections. When growing the PGA, Oracle allocates "heap" memory from the operating system, not shared memory. It is allocated progressively in chunks of about 8K, not in one large chunk. In any event, shared memory allocations do not get rounded up to shmmax, as you apparently imagine. So you have nothing to worry about. If fact, for a system with 4G of RAM, a 1M sort area size should be regarded as very small.

Regards,
Steve Adams

http://www.ixora.com.au/
http://www.oreilly.com/catalog/orinternals/
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-----Original Message-----
From:	Thapliyal, Deepak [SMTP:DThapliyal_at_ea.com]
Sent:	Thursday, July 06, 2000 7:56 AM
To:	Multiple recipients of list ORACLE-L
Subject:	sorting and pga for non-mts

hi dba's

my world has been shattered with horrible thoughts of exactly how pga memory
allocation takes place.

assume u have 4GB ram (your sga is 2gb and u set shmmax to 2gb, remaining free os memory is 2GB)

when a sort occurs .. i know that it will be done in pga..(assume sort requires 1M)

so tell me this .. where is this 1M taken from ?? ... will the pga use the os memory (not shared --> remaining 2GB) or will oracld allocate another shared segment(shmmax) for use by the sort request.

in a nutshell--> does pga use shared memory segments or does it use the remaining os memory(which i think sounds more logical).

the aim is to arrive at a proper sizing of the shmmax parameter. this is for o8i under sol2.6 for non-mts env

tia
deepAk

--
Author: Thapliyal, Deepak
  INET: DThapliyal_at_ea.com

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