Re: Laymans explaination for single level store? -- MIDRANGE-L

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.)"

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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:
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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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