Determine the ORIGINAL PAGE SIZE of an existing database area
Article ID: 9702
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Issue/Introduction
If the definition of a database area has been lost (or there is otherwise some doubt about its definition), and the ORIGINAL PAGE SIZE (a.k.a. space management interval) is not known for sure, use the following process to find out what it is according to the physical database file.
Environment
Release: All supported releases.
Resolution
Go into ISPF and browse the physical file to which the database area maps. In the ISPF display, each database page will appear as one line.
Note that the first line is significantly different to the other lines. This is because it is a SPACE MANAGEMENT PAGE (SMP) and it consists solely of a series of two-byte binary values. Most of these two-byte values will be the same. For example, the first line here in red is the first SMP:
Turn HEX ON and note the first four bytes in the line:
In this case the first four bytes are 00030D41. This is the page number in hexadecimal. X’00030D41’ is 200001.
Turn HEX OFF.
Scroll forward in the file (PF8) and find the next sequential SMP. It will appear similar to the first one, with many, possibly repeating, two-byte binary values. Typically this could be several thousand lines (50 pages) or more.
When the next SMP is found, turn HEX ON again and note the page number. In this example, the next SMP was found here:
The page number is x’0003158B’ or 202123. Now take the difference between these two page numbers, multiply by 2 and add 32.
(202123 – 200001) * 2 + 32 = 4276.
So the ORIGINAL PAGE SIZE clause for this database area is, or should be, 4276.
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