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The SECTIONS option for an Access is used to divide the corresponding data set in multiple physical files. Sectioning a structure reduces internal Enterprise Database Server lock contention when records in the structure are attempting to access these structures. |
The SECTIONS option requires that the EXTENDED attribute be specified for the related data set. You can specify the SECTIONS option for Accesses to disjoint direct and disjoint random data sets only. Accesses for ordered data sets cannot be sectioned.
The data set structure is physically divided in defined sections based on key values specified in DASDL. The following operations effect a file format change and require a DASDL update and control file update:
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Adding or deleting sectioning to an existing Access
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Adding, deleting, or changing the section bounds specifications
Use of the SECTIONS option for a random data set can have an effect on the distribution of data when you specify a MODULUS value. For additional information, refer the the MODULUS option earlier in this section.
Key Bound Values
You section an Access by specifying the SECTIONS option with key bound values. For each key item in the Access, 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 can 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 zeroes.
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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 (zero) values if the key is descending
