Re: Memory sizing - DBA question

Thanks to Michael Abbey, Co-author of Tuning Oracle and everybody else who replied. Things are much clearer now.

msabbey_at_magi.com wrote:

>Sameer, sorry it took so long to get back to you.
 

>utrankar_at_nyc.pipeline.com (Sameer Utrankar) wrote:
 

>>1. All oracle background processes share the same memory ?
>Yes they do, since they are processes thata ctually support the server
>procesees which are shared by the users accessing the database.
 

>>2. Shadow processes also share the same memory as background proceses
>>? Is that why shared memory of shadow process is assumed to be 0 ?
>The shadow processes hook into the shared memory taken up by the
>background processes.
 

>>3. When you run a tool - say sqlplus - shared and private memory of
>>it is considered only once - regardless of how many users are running
>>the same tool - why ?
>In Table 2-2, the figures for sqlplus shared memory (1,781,760) is
>instance wide and only allocate donce. The private portion (393,216)
>is per user. Perhaps the way I presented it is confusing!
 

>>4. I always thought in any computer system, memory is always used by
>>one or more programs. SGA does not figure anywhere in this calculation
>>(and is added later separately) - what does that mean ?
>We added the SGA after the fact cause memory requirements are SO EASY
>to collect for the SGA by the SHOW SGA command in Server Manager.
 

>> Which >process(es) owns SGA ? All background processes ? None ? Why doesn't
>>it figure into memory requirement of background processes ?
>Good question! We do not really care who "owns" the SGA, but let's say
>it belongs to the "oracle" UNIX user.
 

>>On HP machine, using Glance Plus, when I look at memory usage of a
>>process, it shows RSS and VSS parts (Resident and Virtual) and VSS is
>>always more than RSS. Does VSS part include RSS ? Which one do I look
>>at for doing the caculations, similar to tuning book ? VSS or RSS ?
>>VSS figures seem to be more close to the book for sqlplus.
>Sorry, I am unfamailiar with the GlancePlus output. The chapter's
>exercises and sample calculations are designed to illustrate how one
>asseses the amount of memory required for Oracle - not the only way to
>go about doing it. This section was written using HP-UX 9 and HP UX
>Monitor - a rudimentary character -mode predecessor of Glance.
 

>Michael Abbey
 

>co-author Tuning Oracle

Utrankas_at_coned.com (Sameer Utrankar)
212-460-1117 (W) Received on Wed Apr 10 1996 - 00:00:00 CEST