z/OS V1R8 DFSMS Technical Update - IBM Redbooks

2.4 Tape security
This could result in what should be a new migration being skipped when DFSMShsm
considers the data set for migration (see Figure 2-1). If the bit is turned off when the data
set is evaluated, and a migrated copy of the data set is found in the DFSMShsm MCDS, it
may consider that to be a suitable migrated copy, and will revalidate the entry and delete
the data set from DASD. A subsequent recall would then find an old copy of the data set.
Figure 2-1 FSM potential data loss scenario
Using DFSMShsm to manage data set restores manages the situation properly even if, as
is the case, the migrated copy was moved by DFSMSdss.
If in doubt as to whether all data set restores are under the control of DFSMShsm, you
should consider suspending the use of DFSMShsm FSM until resolution is available.
► Apar OA20907 has been opened to provide a patch option for DFSMSdss that changes
the behavior of DFSMSdss to not reset the changed bit if it was found to be on in the
restored copy. This makes its behavior consistent with the invocation of DFSMSdss via
DFSMShsm. You should monitor the status of APAR OA20907.
DFSMS support introduces new options for securing tape data sets using the System
Authorization Facility (SAF). These are designed to allow you to define profiles to protect data
sets on tape using the DATASET class without the need to activate the TAPEDSN option or
the TAPEVOL class. DFSMS also provides options that you can use to specify that all data
sets on a tape volume should have common authorization and that users are authorized to
overwrite existing files on a tape volume.
Chapter 2. Useful information to get you started 9