We are in the process of implementing VM:Tape on Linux for our z/TPF Linux environment.
For this we will be creating Tapes and require the ability to update the TMC with the creating User, ie the Linux requesting User, not the VM Userid of the Linux System.
The TCPIP/Linux command processor creates the MOUNT request that gets issued with the FOR and SAVEFOR options. The FOR UserID is set to the Linux ID (or what is passed in USER to TCPAUTH EXIT). The SAVEFOR UserID is set to the value of REQUESTER (as seen in the TCPAUTH EXIT).
Customer had their VMTLI.USERMAP file specified incorrectly and advised him of needed change and provided sample.
The USERNAME is the Linux server sending the MOUNT request. The REQUESTER is the UserID you want to "own" the tape (will appear in the SAVEFOR option on the generated MOUNT command). This is also the USERID that VM:Tape uses for authentication, what scratch pools it can get tapes from, etc.
Also, found the TCPAUTH EXIT/EXEC is running in "ADDRESS 'CMS'" mode/environment, so, the SET BUFFER command is being interpreted as a CMS command instead of the VMTAPE Primitive "SET".
Recommended a change to place the "SET BUFFER" at the end of the TCPAUTH EXIT, and just before issuing the command, add a line ... ADDRESS 'VMTAPE' ... to switch the mode/environment to VMTAPE.