Re: Accessing a file in memory

["Simon Coulter" <shc@xxxxxxxxxxxxxxxxx>]

h
Hello James,

You wrote:
>I read some of the other responses and started thinking (bad thing on a Monday
>;)), but if you have enough memory to place the files into memory, then why
>aren't they staying in cache?  So I'm not sure if you have enough memory for
>SETOBJACC to work for you.>

Main storage is effectively a cache for DASD on the AS/400 but that is not the 
same as 
the system cache (by which I assume you mean the processor cache?).  SETOBJACC 
will 
provide an improvement if enough main storage can be dedicated to the pool 
containing 
the objects.

>AFAIK, user space is just space and may not reside in memory.  Remember, under
>single level storage disk and memory are the same thing.>

Main storage and DASD are not the same thing.  Single-level store may make them 
appear 
to be the same but that is only from one particular viewpoint.  View storage 
from above 
the MI and it all appears the same.  That is one of the things that makes 
programming 
the AS/400 so simple.  However, the machine still needs to make the 
distinction.  If 
your use of "MAY not" means "MIGHT not" then your statement is true, if you 
mean "CAN 
not" then it is wrong.  All AS/400 objects must be in main storage before they 
can be 
processed -- like any other computer (The S/38 had storage-to-storage 
instructions but I 
don't believe the RISC system do -- they need their stuff in registers).  
SETOBJACC lets 
you tell the system what you care about.

>If you don't have enough memory for SETOBJACC to work for you, I'm not sure 
>that
>making the files into tables would help much either.  You may just be changing
>-what- is being swapped.

In the sense of a table as an array rather than an SQL table it will at least 
improve 
the likelyhood of the needed program storage being available in main storage 
rather than 
on DASD.

Regards,
Simon Coulter.

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