11.8 x/zvsfile—Skip files on a tape. USE x/zvadd INSTEAD.

call xvsfile(unit, number) 
status =zvsfile(unit, number) 

This routine is not needed. Call x/zvadd with the U_FILE optional instead, which is completely equivalent.
x/zvsfile will skip to the file number specified on a tape. If the file number is 0, it skips the tape to the next file.
x/zvsfile requires that the tape file be closed, but it still requires a unit number. If the file has not yet been opened, the unit number can be obtained from x/zvunit . If the file has been opened, it must be closed (with x/zvclose) before x/zvsfile is called, and re-opened afterwards. The unit number obtained from the first call to x/zvunit should be used.
x/zvsfile sets the U_FILE entry in the control block for the specified unit number. The same effect may be achieved by passing the U_FILE optional to x/zvopen directly.

Arguments:

• UNIT: input, integer
  The unit number from x/zvunit of the tape. The file may not be open.
• NUMBER: input, integer
  The file number. The same rules apply for NUMBER as for the U_FILE optional to x/zvopen or x/zvadd. If NUMBER=0, the tape is advanced to the next file. If NUMBER > 0, the tape is moved to the absolute file specified by NUMBER (the first file is file number 1). NUMBER may not be less than zero.