Use the PROTECT command to prevent unauthorized access to your non-VSAM data set. Use the Access Method Services ALTER and DEFINE commands to protect your VSAM data set. These commands are described in z/OS DFSMS Access Method Services Commands.

Data sets that have been allocated (either during a LOGON procedure or by the ALLOCATE command) cannot be protected by specifying the PROTECT command. To password protect an allocated data set, you need to deallocate it first using the FREE command and then protect it using the PROTECT command.

Note that the PROTECT command does not support dynamic unit control blocks (dynamic UCBs). If the device that holds the data set to be protected has been dynamically reconfigured in your system, you will receive a message explaining that the required volume is not mounted. Instead of using the PROTECT command to control data set access the use of RACF® should be considered. For more information about RACF protection, see z/OS DFSMSdfp Advanced Services.

The data set password protection that the PROTECT command provides is much weaker than the protection provided by RACF. Many of the reasons for that are stated in the data set password section in z/OS DFSMSdfp Advanced Services.