Why after a reorg of a LOB table space, the space of the VSAM LDS data set remains the same and the data set is not re-allocated?.

Document ID : KB000021597
Last Modified Date : 14/02/2018
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Question:

During a CA Rapid Reorg for DB2 for z/OS execution against a LOB table space, the underlying VSAM LDS dataset is not re-allocated. How is the free space reclaimed?

Answer:

After a reorg of a LOB table space its size does not change. This gives the impression in CA Rapid Reorg that the space is not freed in LOB table spaces as they are not deleted and re-allocated. The internal pointers are just updated but the space remains the same as before the reorg. CA Rapid Reorg of a LOB table space will only compress the existing LOB data, in other words an unload and reload of data does not occur. Data rows are rolled up eliminating any unused space similar to a compress of a PDS.