VMS Help MOUNT, Qualifiers, /RECORDSIZE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

       /RECORDSIZE=n

    Specifies the number of characters in each record of a magnetic
    tape volume.

    The parameter, n, specifies the block size in the range 20 to
    65,532 bytes if you are using OpenVMS RMS, or 18 to 65,534 bytes
    if you are not using OpenVMS RMS.

    You typically use this qualifier with the /FOREIGN and /BLOCKSIZE
    qualifiers to read or write fixed-length records on a block-
    structured device. In this case, the record size must be less
    than or equal to the block size specified or used by default.

    Use the /RECORDSIZE qualifier when mounting magnetic tapes
    without HDR2 labels (such as RT-11 magnetic tapes) to provide
    OpenVMS RMS with default values for the maximum record size.

    Example

    In the following example, the magnetic tape is mounted on MTA0
    with a default block size and record size of 512 characters:

    $ MOUNT/FOREIGN/BLOCKSIZE=512/RECORDSIZE=512 MTA0: