If you are restoring any of these types ( unmovable, direct, or absolute track) of data sets by preallocating them, the size and location of the extents on the dump volume and on the restore volume should match. Restoring a data set to a larger preallocated data set can cause problems because of the extraneous data beyond the end of the original dumped data. If the preallocated data set is too small, DFSMSdss deletes it and reallocates a new data set. The allocation may fail, or it may result in a new data set with a different configuration (for example, fewer volumes). The latter situation can cause problems processing the data set.

For unmovable data sets (those allocated as ABSTR, PSU, POU, or DAU), a preallocated data set is restored if the extents match and the REPLACE or REPLACEUNCONDITIONAL keyword is specified. Even if the extents do not match, the data set is restored if you specify both the REPLACE and FORCE keywords or the REPLACEUNCONDITIONAL and FORCE keywords. When an unmovable data set cannot be restored, the extents of the data set on the source volume are listed so that you can take action to restore it.