Unloading compressed data

You can unload compressed rows from an image copy data set only when the dictionary for decompression has been retrieved. If a row is compressed and the dictionary pages have not been read when the row is encountered, the UNLOAD utility ignores this row, issues a warning message, and increments the error count.

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If the error count reaches the limit that is specified by the MAXERR option, UNLOAD terminates with an error message.

If the image copy data set is an incremental copy or a copy of pieces that does not contain a dictionary, the FROMCOPYDDN option can be used for a DD name to concatenate the data set with the corresponding full image copy that contains the dictionary. If SYSTEMPAGES YES is used, a dictionary will always be available in the incremental copies or pieces.