You can define data set passwords for non-VSAM data sets, but not for VSAM data sets. Passwords are ignored for all system-managed data sets, new and existing. However, passwords can still be defined for system-managed data sets.

IBM recommends not using passwords for data sets. The security provided by data set passwords is not as good as security provided by RACF. See z/OS DFSMSdfp Advanced Services.

The system ignores data set password protection for system-managed data sets.