If you want to write USS files from Acquire then the file system to where they will be written must be mounted before you try to do so. You may choose to get your Systems Programmer to have it mounted automatically as part of the IPL process, or you can use a job is provided in the sample JCL library to do this, called RUNCKMNT. This runs a Rexx routine called CKMOUNT, also supplied in the JCL library, to issue a mount for the file system. The CKMOUNT Rexx routine must be given two parameters, the name of the USS file system (the z/OS dataset name) and the name of the mount point which Acquire will be told to use.