Some data sets on your system may contain records past the last-used-block pointer in the data set’s VTOC entry. This could be a result of a data set not being properly closed or an application that accesses data in such a way as to bypass the updating of this field. In this case, special consideration needs to be given to these data sets as DFSMSdss recognizes this block pointer as the end of the used space in the data set and, therefore, the end of the real data.

Using the ALLDATA or ALLEXCP keyword will result in all the allocated space being dumped for applicable data sets. This includes all the data up to the last block pointer as well as all the data to the end of the allocated space. However, whether or not all the data is restored depends on data set characteristics and device characteristics during the restore. For example, if the data set must be reblocked (either because the target is an unlike device, the REBLOCK keyword is specified, or the data set is marked reblockable) only the used space will actually be restored. This limitation is due to the fact that any residual data (that is in the unused portion of the data set) will likely have different characteristics than the real data (that is in the used portion of the data set). This inconsistency would result in data incompatibilities causing the restore to fail, and thereby inhibiting the ability to restore the real data. Because of this, DFSMSdss will only restore the data in the used portion of the data set when the data characteristics must change.

If you require that all of the unused space is restored, then you should ensure that the data set is restored to a like device type and not reblocked or compressed. (Compress is the default for PDS data sets on restore unless you use the NOPACKING keyword.) In this case, the characteristics of the data do not change, and DFSMSdss will restore all the allocated space.