Memory sizing - DBA question

From: Sameer Utrankar <utrankar_at_nyc.pipeline.com>
Date: 1996/04/02
Message-ID: <4jq90h$sa_at_news.nyc.pipeline.com>#1/1

I am assuming readers of this post have read 'Tuning Oracle' from Oracle press. I am confused about Memory requirement calculation done in the book (page 26, chapter 2).

This is what is done for memory requirement calculation in the book :

1. Shared memory of all the Oracle background processes is considered only once.
2. Private memory of each background process is considered separately.
3. For tools (such as sqlplus, runform) shared and private memory is considered only once - regardless of number of users running the tool.
4. Shared memory of tool's shadow process is assumed to be 0.
5. Private memory of tool's shadow process is considered taking number of users into consideration.
6. SGA is NOT considered in this calculation at all and is added later separately.

My questions are :

1. All oracle background processes share the same memory ?
2. Shadow processes also share the same memory as background proceses ? Is that why shared memory of shadow process is assumed to be 0 ?
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 ?
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 ? Which process(es) owns SGA ? All background processes ? None ? Why doesn't it figure into memory requirement of background processes ?

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.

Any help would be greatly appreciated.

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utrankar_at_nyc.pipline.com (Sameer Utrankar) All of us can't be heros. Someone has to sit by the curb and clap as they go by. Received on Tue Apr 02 1996 - 00:00:00 CEST