VMS Help PIPE, Description, Pipelines and TEEs, File Access Methods in a Pipeline  *Conan The Librarian (sorry for the slow response - running on an old VAX)

    A pipeline segment command can only use the RMS sequential file
    access method to read and write to the pipes. Certain OpenVMS
    utilities may access their input and output files using methods
    other than sequential access. These operations are not supported
    in a pipeline, and will fail, as in the following example:

    $ PIPE CC/NOOBJ/NOLIS TEST.C | SEARCH SYS$INPUT/WIND=(1,1) "%cc-w-"

    %SEARCH-F-RFAERR, RMS error using RFA access
    -RMS-F-RAC, invalid record access mode

    In this example, the /WINDOW qualifier for the SEARCH command
    requires the relative file access method.