Please tell me how single-level storage works in the AS/400 (not too techie please).
I paid a visit to the iSeries Information Center and found this little narrative... Kenneth
On the AS/400, main memory is called main storage. Disk storage is called auxiliary storage. You may also hear disk storage referred to as DASD (direct access storage device).
Many other computer systems require you to take responsibility for how information is stored on disks. When you create a new file, you must tell the system where to put the file and how big to make it. You must balance files across different disk units to provide good system performance. If you discover later that a file needs to be larger, you need to copy it to a location on disk that has enough space for the new, larger file. You may need to move other files to maintain system performance.
The AS/400 system takes responsibility for managing the information in auxiliary storage. When you create a file, you estimate how many records it should have. The system places the file in the best location for good performance. In fact, it may spread the data in the file across multiple disk units. When you add more records to the file, the system assigns additional space on one or more disk units.
The system uses a function that is called virtual storage to create a logical picture of how the data looks. This logical picture is similar to the way we think of the data. In virtual storage, all of the records that are in a file are together (contiguous), even though they may be physically spread across multiple disk units in auxiliary storage. The virtual storage function also keeps track of where the most current copy of any piece of information is-in main storage or in auxiliary storage.
Single-level storage is the unique architecture of the AS/400 that allows main storage, auxiliary storage, and virtual storage to work together accurately and efficiently. With single-level storage, programs and system users ask for data by name, not by where the data is located. Now lets move one more step up the technical ladder for a little more information! Kenneth
Read about Single-level Storage
I hope this answered you question!
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This was first published in October 2001