The set structure is logically divided in defined sections by means of multiple root tables. The sections provide greater access to the set by increasing the number of root table locks that the system can hold simultaneously.
The Accessroutines divides the physical set file in sections. The following operations effect a file format change and require a DASDL update, control file update and reorganization:
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Adding or deleting sectioning to an existing set
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Adding, deleting, or changing the section bounds specification
Key Bound Values
You section a set by specifying the SECTIONS option with key bound values. For each key item in the set, you declare the key range by specifying the
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Upper bound value for ascending keys
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Lower bound value for descending keys
You separate each section specification with a semicolon (;). The maximum number of sections you can declare with multiple bound values is 511. The result is that each section contains records whose key values lie within a specified key range. A key item with a REAL(I) or REAL (I,J) type cannot have a key bound value greater than 2**39 – 1.
Characteristics of the key range are
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If the size of the specified key value is less than the size of the declared numeric, real, or field key item, the system pads the value on the left with zeros.
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If the size of the specified key value is less than the size of the declared ALPHA key item, the system pads the value on the right with
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Hexadecimal F values if the key is ascending
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Hexadecimal 0 values if the key is descending
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