DFSMShsm attempts to process data sets with invalid formats. If an error is detected, the operation fails, and an error message is issued. If DFSMShsm does not detect an error, the results of a DFSMShsm operation are unpredictable and could result in deterioration of the condition of the data set. The following data sets can cause unpredictable results:

• Partitioned data sets with invalid directory block entries
• Variable-length-format data sets with embedded, nonstandard records
• Data sets with embedded physical blocks with a size not consistent with the block size indicated in the data set VTOC entry.
  Attention: With DFSMSdss as the data mover, uncataloged user data sets can be lost if the user tries to direct recovery of a cataloged data set with the same name to the same volume on which the uncataloged data set resides.