VMS Help MERGE, Output File Qualifiers, /FORMAT, Qualifier Values  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 BLOCK_SIZE:n

    Specifies the output file's block size, in bytes, if you have
    directed the file to magnetic tape. You can also accept the
    default. If the input file is a tape file, the block size of
    the output file defaults to that of the input file. Otherwise,
    the output file block size defaults to the size used when the
    tape was mounted.

    Acceptable values for block size n range from 20 to 65,532. To
    ensure correct data interchange with other Compaq systems,
    however, specify a block size of not more than 512 bytes. For
    compatibility with systems that are not made by Compaq, the
    block size should not exceed 2,048 bytes.

 CONTROLLED:n

    Specifies variable with fixed-length control (VFC) records in the
    output file.

 n

    Optionally indicates the maximum record size (in bytes) of the
    output records. The maximum record size allowed depends on the
    file organization.

    Sequential files          32,767
    Relative files            16,383
    Indexed-sequential files  16,362

    These totals include control bytes. If you do not specify the
    maximum record size, the default is a length large enough to hold
    the longest output record.

 FIXED:n

    Specifies fixed-length records in the output file.

 SIZE:n

    Specifies the size, in bytes, of the fixed portion of VFC
    (CONTROLLED) records, up to a maximum of 255 bytes. If you do
    not specify SIZE, the default is the size of the fixed portion of
    the first input file. If you specify this size as 0, OpenVMS RMS
    defaults the value to 2 bytes.

 VARIABLE:n

    Specifies variable-length records in the output file.