Re: AIX 4.2 and Oracle 7.2/7.3 SGA/PGA and virtual memory

Jens Wartenberg wrote:
>
> Hi.
>
> Can you help me with a question regarding aix-behavior?
>
> SHORT:
> ------
> I understand that AIX uses almost all not actively used RAM for
> "disk-cache" for the jfs (not using raw devices!). I am hovever not sure
> which of the following is "true":
>
> Examples: MB
> --------- ----
> RAM: 128
> Paging space: +256
>
> Assumption 1: (I believe this is "true")
> -------------
> Base consumption of RAM (SGA, AIX etc.): 50
> ACTIVE usersessions (30sessions*3MB*50%): 45
> --
> 95
> Available for "disk-cache" (128 - 95): 33
>
> Assumption 2: (I hope this is not "true")
> -------------
> Base consumption of RAM (SGA, AIX etc.): 50
> Usersessions (ALL) (30sessions*3MB*100%): 90
> -----
> 140
> Available for "disk-cache" (128 - 140): (none)
> (I should be able to see more than very little paging activity when
> using vmstat).
>
> If assumption 1 is "true", I will allocate 33MB ram more the Oracle
> SGA/PGA (using the values of the above example).
> If assumption 2 is "true", I will probably recommend the customer to buy
> more RAM.
>
> LONGER VERSION FOR UNDERSTANDING:
> ---------------------------------
> I am working on getting the most out of Oracle-based applications in
> AIX-environments. The applications are integrated (MPS, Economy etc.) to
> cover 90%-95% of the needs of manufacturing companies. The main tables
> contain 1-10 million rows, and the database has a size of 4-14GB.
>
> Most of my customers has 2-4 AIX+Oracle sessions pr. user, so the most
> frequently used functions are "at the fingertips". This means, that most
> of the time 50%-70% of the sessions are "sleeping".
>
> My problem is, how I should size the Oracle-SGA/PGA with this memory-use
> in mind.
> MY AIM IS to use the RAM available for active Oracle in stead of for
> aix-disk-cache, as Oracle should manage the cache more efficient as a
> result of having different priorities for index-data and table-data. Aix
> is of course not able to prioritize disk-cache in this manner.
>
> Most of my customers seem to have to little memory allocated to SGA/PGA
> (13-25MB), resulting in a lot of I/O activity which of course is bad for
> performance.
>
> I HAVE tried to study some books on the subject, but I am not sure about
> the behavior.
>
> Thank you in advance for any comment.
>
> Regards
>
> Jens Wartenberg
> Wartenberg Industri Data
> Denmark

Have you considered using Multi-threaded server in your calculations?

Steve Phelan. Received on Mon Mar 03 1997 - 00:00:00 CST