Re: Laymans explaination for single level store?

[Vernon Hamberg <vhamberg@xxxxxxxxxxx>]

This first link is from PartnerWorld's stuff - seems pretty good, as it is 
written for folks coming from other platforms. Covers other basic stuff, as 
well.

<http://www-1.ibm.com/servers/enable/site/porting/iseries/overview/overview.html>

This next is probably not "laymanic" enough, but it's from the V5R3 System 
Handbook. But maybe you can pull something out of it. I think of this 
concept as "all storage, whether main memory or disk, is lumped together - 
you don't need to figure out how to divide it up, as with SQL Server and 
DB2 on Windows, and developers don't need to worry about memory segments 
(64K chunks of memory in DOS, e.g.)"

========================================================
Single-level storage

Application programs on an iSeries server are unaware of the underlying 
hardware characteristics, because of the iSeries layered architecture 
approach, Technology Independent Machine Interface (TIMI). TIMI frees 
application code from worrying about processor technology, such as moving 
from 32- to 64-bit or Complex Instruction Set Computing (CISC) to Reduced 
Instruction Set Computing (RISC).

The concept of single-level storage means that an application does not deal 
with storage device specifics. The knowledge of the underlying 
characteristics of hardware devices (in this case, main storage and disk 
storage) reside in the System Licensed Internal Code (SLIC). All of the 
storage is automatically managed by the system. No user intervention is 
ever needed to take full advantage of any storage technology. Programs work 
with objects. Objects are accessed by name, not by address.

iSeries servers are commercial servers designed to handle many programs and 
users running simultaneously. Single-level storage enables very high-speed 
switching between active and idle programs and users as compared to other 
operating system architectures. It contributes directly to iSeries high 
performance characteristics.

The iSeries server address size is vast. iSeries models can address the 
number of bytes that 64 bits allows it to address. The value 264 is equal 
to 18,446,744,073,709,551,616. Therefore, the iSeries models can address 
18,446,744,073,709,551,616 bytes, or 18.4 quintillion bytes. To put this 
into more meaningful terms, it is twice the number of millimeters in a 
light year. Light travels at approximately 6,000,000,000,000 miles in one year.

Single-level storage also enables another extremely important iSeries 
customers benefit?object persistence. Object persistence means that the 
object continues to exist in single-level storage (unless purposely deleted 
by the customer). Memory access is extremely fast. A typical server 
requires that information be stored in a separate file system if the 
information is to be shared or retained for a long time. The maintenance 
and awareness of the separate location can impact the total cost of 
ownership of the application.

Persistence of objects is extremely important for support of 
object-oriented databases for data accessibility and recovery. Objects 
continue to exist even after their creator goes away. iSeries models are 
uniquely positioned to exploit this characteristic of object persistence. 
Customary systems use a less elegant mechanism that requires them to store 
their persistent objects in a separate file system, with all the attendant 
performance implications of application and operating system implementation.
================================================

And a little more from the same book:
================================================
Parallel data access

Queries returning or requiring DB2 UDB for iSeries to process large amounts 
of data require significant input/output (I/O) activity. Due to the 
iSeries' single-level store architecture, this data is often spread across 
many physical devices. The parallel data access feature allows multiple 
internal DB2 UDB for iSeries tasks to be activated for each physical 
device, allowing DB2 UDB for iSeries to transfer data from disk to memory 
faster than with the previous single task I/O architecture.
=================================================
At 06:49 PM 11/23/2004, you wrote:
> Can anyone point me to a laymans explanation of what single level store is 
> all about.
>
> I'm trying to educate some folks in our office and some of them are not 
> geeks like me.
>
> Thanks!
>
> david
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