Input and output for the Unload function

The Unload function is invoked by the UNLOAD command in the HFPSYSIN DD control statement to unload multiple DEDB areas to QSAM data sets.

To reorganize areas of a DEDB, only the IMSACB library is required. If you want to change the definition of a DEDB, for example to extend an area by increasing any of the sizes of UOW, IOVF, and CI, you also need to specify the NEWACB library that has the DMCB member of the new DEDB definition. The SORT program can be invoked internally to achieve better SORT performance by eliminating the SORTIN and the SORTOUT file I/O operation. When the unload process is completed, IMS HP Image Copy can be invoked internally to create the image copies.

If you enable the IMS catalog and the IMS management of ACBs, ACB definitions are retrieved from the IMS directory instead of IMSACB and NEWACB libraries.

The following figure shows the input and the output for the Unload function.

Figure 1. Input and output for the Unload function
This figure depicts the typical input and the output data sets for the Unload function. Details about the data sets are described in this topic.

The Unload function can read and unload the following image copies of a DEDB:

  • Standard image copies that are created by IMS Image Copy utility (DFSUDMP0) or IMS HP Image Copy
  • Compressed image copies that are created by IMS HP Image Copy

When image copies are provided as input data sets for the Unload function, new image copies cannot be created after the completion of the unload process.