DFSMSdss relies on a SYSDSN and SYSVSAM enqueues for physical dump operations. By default, DFSMSdss attempts exclusive enqueues during physical dump. As long as the data set is not mounted at dump time, the exclusive enqueues provide sufficient serialization. If the data set is mounted before the physical dump job begins, z/OS® UNIX will have the zFS data set allocated and opened. Allocation and open processing will have obtained SYSDSN and SYSVSAM enqueues. DFSMSdss will therefore not be able to obtain the exclusive enqueues.

Physical dump of mounted zFS data sets is not recommended because quiesce is not available during a physical dump. If you specify the TOL(ENQF) keyword during a physical dump, the internal control information and data inside the zFS can change during the dump. This can result in a dumped data set that contains a zFS data set that might not be usable after you have restored it.