When you access:

  node"username password"::"TASK=filename"

then there are a limit on 16 characters on the filename.

Solutions:

1)  Enter the file in the NCP database.

    $ MCR NCP
    NCP> DEFINE OBJECT shortname NUMBER 0 FILE filename
    NCP> EXIT

    access node"username password"::"TASK=shortname"

2)  Define a logical for file.

    $ DEFINE/SYSTEM shortname filename

    access node"username password"::"TASK=shortname"