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3.12 Ghost Areas
In cases where the size of the SDS array is not an even multiple of the chunk size, regions of excess array space beyond the defined dimensions of the SDS will be created. Refer to the following illustration.
FIGURE 3e - Array Locations Created Beyond the Defined Dimensions of an SDS
These "ghost areas" can be accessed only by SDreadchunk and SDwritechunk; they cannot be accessed by either SDreaddata or SDwritedata. Therefore, storing data in these areas is not recommended. Future versions of the HDF library may not include the ability to write to these areas.
If the fill value has been set, the values in these array locations will be initialized to the fill value. It is highly recommended that users set the fill value before writing to chunked SDSs so that garbage values won't be read from these locations.
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HDF User's Guide - 05/19/99, NCSA HDF
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