In earlier versions of Adaptive Server, the maximum value allowed for the number of preallocated extents was 31. In Adaptive Server version 15.5 and later, the maximum values of preallocated extents has been increased to 32.
Using a value of 32 for the number of preallocated extents has a special significance for configuration, and impacts the space allocations Adaptive Server performs internally. If you set the number of preallocated extents to 32, Adaptive Server attempts to reserve an entire allocation unit of extents for utility operations that use a large-scale allocation scheme of space reservation, such as bcp in and select into.
Using the maximum number of preallocated extents can greatly improve the performance of these utilities, particularly when you run them in parallel. Using a value of 32 greatly increases the likelihood that each engine running the utility can work independently on its own allocation unit without interference from other engines.